What is the name of your state (only U.S. law)? Ohio
I need help with getting a divorce. I also want to have joint custody of our kids. We are currently separated ( not legally separated ) and I live in a separate home. I also want to make sure that she can not leave the state and go live somewhere else. What are my options?
Joint legal custody (which basically concerns decision making and responsibility for the kids) is becoming more and more common in most states. In some states, it's the default - that means that the other party has to prove you're unfit in order to get sole custody.
Joint physical custody is harder. While it is also the default in a few states, it is easier for the judge to give one parent primary physical custody. For the best chance of joint physical custody, the parents need to live close enough that the kids' lives won't be disrupted any more than necessary. They need to either live in the same school district or one has to be willing to drive to the kids to the school district where the other parent lives. Both parents need to be able to demonstrate sufficient maturity to work with the other parent on parenting issues.
You cannot keep HER from leaving the state, but you can keep her from taking the kids to another state. It's fairly straightforward in most cases, but you need to act quickly. Once you file for divorce, you ask for a ruling that neither of you moves the children out of state (make sure it works both ways so it doesn't look like you're trying to pull something). If there's a risk of flight, it is possible to get a ruling that she can't even take the kids out of state for visits (my ex had a ruling from her first divorce that she couldn't even leave the county with the kids for dinner). Unless there's real risk of flight, though, IMHO, you want to be very reasonable since it is likely to lead to a better resolution in the end. A rule against moving out of state with the kids is probably sufficient in most cases. BTW, check the divorce docs. In some states, that rule is applied automatically as soon as one party files for divorce.
You have kids and want to keep joint custody. The fact that you're asking the question here suggests that it may be contested. I would strongly encourage you to consult with an attorney. There's a lot at stake (unless the kids are almost adults in which case the issue isn't as important).