In the Ideal Stepmom World...

Updated:
What I wish I would have known. What I wish I would have been told. What I wish had been handed to me in a guide, preferably in checklist format. Here are the ideals you should start with or work towards for your stepmom world, especially if it's not too late and you're getting ready for your stepmom life:

• If you're going to support your husband's court battles or be involved AT ALL, which by being his wife who loves him often can mean you are involved and can't just ignore the hell in his world, hire the best lawyer possible for your husband (if you're the only one with money after his years of divorce, alimony and custody) or simply help him hire the best lawyer possible by doing research, setting up interviews, and talking to people who know people, and then use up your money to get the best custody orders possible- Right from the start, out of court or in court. Erase the horrible agreement he made with her when he was clueless and trusted her to be a decent human being, which of course didn't happen, and just take care of it right off the bat. If out of court, do a home study immediately so that a professional can give an entire report about how your home and parenting are better than the other home. Find a pro-father out of court mediator, and do your research and call around before agreeing to it. Use your mediator and her mediator if there's a choice disagreement. If you're in a litigious situation, getting a great lawyer up front will save you so much more pain down the line-  your husband's pain of either losing his children, dealing with the dumbest agreements a mediator could ever turn into a template that they then pass on to every case, or continued court battles with a jealous idiot + your pain of dealing with it too, as you will factor into the crappy agreement that didn't even factor in the schedules of the actual parents, and watching him in pain for YEARS. Oh, and get an agreement that means that you will deal with her less. Even though you're not there, you can be factored into the agreement somehow. Yeah, it legitimizes you, but down the line you feel trapped. 
• Speaking of which, get a copy of their agreement and study it for days. Make a list of questions and warn your boyfriend/husband that you need the time to discuss this. Set up a time so he can prepare himself, as he could get defensive. He was likely steamrolled into this agreement, didn't know that some things would turn out the way they did, and didn't think through every part because the courts and even lawyers, if he even had one, don't give you enough time to review the agreement you're signing before you sign it. Be gentle with him and understanding that he may not have seen the repercussions of what he signed, especially not in light of a remarriage to another woman who may have other plans in mind. BUT you need to know. In a remarriage, this is just as important as looking at the finances up front. You need to know what you're signing up for, what you can expect for holidays, who gets who's insurance, retirement, pension, assets... Their custody agreement becomes your life. He may not think so at the beginning, oh but how you will realize this as time goes on. You need to see it for yourself and not depend on his memory of it, or his occasional moments of information sharing. (He will say he told you everything, but he told you everything he thought was important for you to know. Trust me, there's more that you would be concerned about. And you need to know about it AND understand it.) And honestly, it's possible he missed a few things. Regardless, his contract with his ex is now your life's/family's contract.
• Although you want to help your husband as much as possible and you feel and see his pain on a daily basis, do everything possible to cut yourself out of exchanges and ALL interactions with the children's mother. Just-do-it. Just get out of the mix. First of all, you may be helping, but you will resent it further and further down the line. Second, do you really want to interact with her? Your husband's ex? Really? Do you even want to SEE her? Even if you're doing OK with her now, things can change. It's documented (court statistics) that different events can cause an ex to change their demeanor and turn into a scary monster (events such as you getting pregnant, their remarriage to a guy with money to support her court efforts, your marriage, mental illness, and who knows). Didn't see that coming? Now you do.
•  Live in another town. Not the same town. Live in the town next door. Live somewhere where you don't run into her EVERYWHERE. You will end up with the habit of circling parking lots to see if her phantom car is there, or her family member's cars. You will think you see her down the next aisle, but it's really just someone else. You will avoid places she goes, even though you always went there. Just live in another town. A couple of miles won't hurt you. It may be slightly detrimental in court, so come with specific mileage of your distance from the children's schools. (Mothers can try to make it look like you moved "a whole town away!!!" to prove you clearly don't care about the children because you're not sharing the same house or street or neighborhood, and mediators show bias as if the town that's only 5 miles away is in another state. I kid you not, as we experienced this by living in "another county" which was on the border of the town of the kids and just 2 miles beyond where they lived with their mom. So arm your husband with the exact mileage that the next town over is from everything, to bring everything back into perspective. Especially when your distance from their schools is actually CLOSER than their own mother's, even though you're in the next town! Or something similar, like you live in a town with better schools, or you live closer to their future middle school or high school...Anything that erases the argument that you "moved away", which kids are also easily influenced by, as well, since their worlds are so relatively small until they start going to and from your house and realize it's not that far and maybe even closer to cooler stuff...)
• Get a HUGE house. Get the biggest house possible. Can't afford to buy a big house? Then DON'T buy a house! RENT the huge house until they're old enough to move out, or at least one of the kids is old enough to move out, or until you CAN buy the HUGE house. Why? You need your space. They will need their space when they are teenagers, too. But YOU need your space. And, you'll win custody fights purely based on the kids wanting their own rooms. Custody doesn't go to the parent who parents best or even looks good in court- It goes to the parent with the most space who allows them individual rooms or cool toys. Sounds petty? If you don't want to think about the crap that is family law decisions or you haven't encountered the truth yet, then focus on how you need your space. Your stepkids, although cute now (maybe, if they're young and not manipulated yet), will drive you up the wall more and more as you learn of their peculiar, strange "habits" (usually involving dirty socks and underwear...or, a lot worse...). Try as you might, you won't be able to change their peculiar, weird habits and you'll even maybe find that your husband somehow gave those habits to them... So it's best to give them, and you, SPACE. You will need it so badly. In fact, just get a duplex. One for them, one for you. When you can't stand them, retreat. Relax. Watch your favorite movies. Stay away from them, because the more you're angry, the more they don't want to come over and see their dad, which hurts you even more as you see your husband's pain. So, if you give yourself space, and the space to give yourself space, you'll fare so much better and make everyone happier. It's a win-win.                         Buying tips: If you get the sense that the house is "cozy", don't take it. That means it's WAY too small. If you get the idea that you'll be able to move up later, don't make that foolish mistake- your money will be gone before you know it, due to wonderful things like the economy, taxes, childcare, child expenses, child support, summer camps, a car and insurance for the teenager, college, family vacations, braces, etc. Don't plan on a move up later. You may not be able to until they're out of the house, due to money or custody orders (which can change to God-only-knows what). And don't buy a smaller house because you're concerned about the workload of maintaining it. You just need the space- even in a small house with kids, you'll be amazed at how your house is never clean. At least in a bigger house, your family's messes can be spread out or cut off from your favorite areas, rather than condensed and that much more apparent, often in the shape of piles and layers of grime. You will need your "sane" or clean areas that you will feel an ounce of control over.
• If their mom is involved in their lives, let her be in their activities. Keep your own activities. If she isn't involved, go for it. If she isn't involved in a particular activity, go for it but still be warned that she will cause drama after she sees how you've become involved. You can't escape it, and she'll either spread lies about you to others (oh well, because you were there first) or she'll just stop allowing the kids to go. It will hurt you, so be ready for it. Or, just don't volunteer for things involving your stepkids no matter how much you want to show them that you are capable of things and other people do like you. Volunteer with other people's kids or only your own, unless your stepkid specifically asks you to be involved. I think that's the one exception. Still, be prepared for their mom to not like that at all, and your stepkid to one day hate that activity after their mom's jealousy invaded their brain. And, if you're in my type of wonderfully volatile situation, you may even get their mom suddenly caring about that activity and turning it into some sort of "I can top you" war where she manages to get in your face at every turn! Oh, the joy. 
• Get some pets. Right away. Make it a wedding gift. One probably won't be enough. Get some pets that can give you a myriad of excuses for leaving the house or retreating to your bedroom, like a dog that allows you an ongoing excuse for miscellaneous activities like running, hiking, short walks, long walks, dog parks, grooming... And a cat or two for cuddling when you feel left out of the family affection or your husband needs to cuddle the kids and not you. (Get over it. Get a cat. They're super soft.)
• Keep your friends or get back in touch with your friends. You will easily be sucked out of your former life by a new love and his kids. His world is so full of...life (and drama...and baggage...) that it's easy to get lost in it and forget about you, and especially your old life. Then, at some point you'll realize you lost who you were and all your friends. Do your part to keep your friends. They will need you, you will need them. Don't scare them off with too many stories about your new stepmom world, which is easy to do, because they just won't understand. But, you still need them. So keep up the lunch and dinner dates and going out. You need it, and you'll need it later. They will need you when they have kids and other big life events. They're just confused by your current position in life, as they probably have already stated they would never choose this path. Did your marriage take you out of the area and you're no longer around your friends? Try to keep in touch, but if you can't physically meet up with them, then it's time to focus on making new friends. Make the effort. Join some groups, clubs, volunteer for something, etc. It will take time, so the sooner you join and get going, the better. Include your husband, or not. Just get moving on making new friends so that you have people to physically go out with, to meet up for drinks with, and to just get out with. You will need it and long for it. You will want to go do things that your new family won't care about, and it will be a fight to get them to enjoy it even if you talk them into it. But you also need someone that allows you interaction and discussion outside of your twisted world of family and in-laws. Can't make friends beyond the virtual kind? Go to meetup.com. Look for stepmom groups, book clubs, adventure clubs, couples clubs, religious clubs, etc. 
• Have a good job with a positive work environment. If you're in a job that makes you feel bad about yourself or makes you more stressed than you should be, get out before you become a stepmom. A bad job makes you that much more unhappy, and that much more unable to handle your new life and all it's insane responsibilities that no one in their right mind would commit to. You'll suddenly have kids, and need to use sick days and vacation days for the kids when your husband is working. You'll suddenly need to leave early to pick them up or come in late to drop them off. When you're in a toxic work environment, people will use that against you or your bosses won't allow you the flexibility you'll need. But most of all, your life will be stressful at home and at work, and you'll find yourself drowning. You need to make one of your primary environments less stressful as you navigate your new life and role and family. Getting a new job may not sound easy, but it's necessary if you're going to take on the Stepmom title.
• And the most common recommendation already out there: Get some hobbies. Keep yourself busy. Maintain a partially separate life where your stepkids and your husband's ex don't permeate the experience. Do some hobbies that make you feel accomplished and give you self-worth. You will need that as a balance to the way that stepkids and an angry mom can make you feel or kill all your hopes of things being easy or normal. It may seem like you're doing well as a volunteer for their school or their activities, but you may at one point feel like there's no escape to the bizarre world you're stuck in. If you have external activities, you will have more balance and perspective.
• Never, ever think that spending your money on your stepkids will change their actions, behaviors, and attitudes to and about you. It won't make a damn difference. They cannot connect money spent on them (that you earned and chose to spend on them) to care. Regular parents deal with this, there are tons of articles out there about how middle class kids (and beyond) have a sense of entitlement, and you'll have even less impact than a regular parent even if you buy them everything they've ever wanted and cook them their favorite, unhealthy meal on a daily basis. It won't matter. Their mom's opinion, and her family's, is what matters. You can go ahead and spend your money on those tickets or those clothes, but they won't remember that you did it for them or gave those things to them. You have to accept that, or not spend the money. You can focus on how you exposed them to culture and special events or helped shape their life into what it will become, but you can never expect them to connect your money and effort spent to a positive connection with you. And if you try to make them see the connection between care and time and earned-money spent, you'll find out that it is simply what they expect since you are their caretaker. It doesn't make you any more valuable, and could even be turned into "she tries to buy my affection." (Still, you CAN make them say thank you. You're never wrong for asking for manners and gratitude, just like any normal parent would. I'm not talking about house rules and repercussions for snotty behavior. Just your expectations.)

You may not be able to accomplish all of the above, but it's what I have realized would have made everything a whole lot smoother for all of us.There already exists a lot of "do's and don'ts" for stepmoms out there. I'm tired of those lists. They are specifically geared towards how to treat and think about your stepkids and their mom and how to change you and your thoughts and emotions. Let's be real and talk about things you can control in your environment that work out better for everyone, rather than your specific behavior and interactions- which are honestly pretty hard to control when everything's unnaturally insane or twisted. Notice that the only "thought" change I suggested was the last bullet point, and I struggled with whether to put that in. I struggle with that one the most! The other options are things you can change about your environment, in the ideal world....

In the ideal world, spend all your money on spa days, yoga classes, a sprawling house with a forest and mountains or the ocean in the backyard,  a vacation home, and lastly, a super crazy expensive lawyer that handles absolutely all interactions with your husband's ex.