I’m ultimately going to divorce. I understand that there needs to be a period of separation before the courts grant a divorce. Is there a legal definition of "separation" which I should be aware of?
Voluntary separation is when two parties agree that they need to go their own ways. Even though it may not start out as a "voluntary" situation, the parties can eventually come to a mutual agreement that separation was inevitable.

Most states require that you live separately for the statutory period of time. This means no cohabitation. Separation means residing (and sleeping) in different locations at all times. Separate bedrooms in the same house do not constitute a separation.

The courts distinguish between separation and "desertion", which is when one of the parties leaves without the intention of returning. If the other person forces you to leave, that is "constructive desertion." You won’t be penalized by the court if you leave for your own protection or that of the child(ren).

When is separation the appropriate course?
Before you think about separation, ask yourself if you’ve taken all reasonable steps to make the marriage or home situation better by working together. Did you try sitting down calmly with your spouse to discuss the situation? Did you try counseling, either individually or as a couple? Talking to a psychologist, social worker, pastor, or trusted family friend may provide the necessary medium for working out differences.

If you have children, consider the impact of staying (or leaving) on them. And never bring them into the fight. Always remember: Children may be resilient, but their armor is only so thick. Children know more, see more and hear more than you think. If staying together is creating an emotionally troubling situation for them, perhaps separation is the best option.

If I decide to go ahead with it, how should I go about separating from my spouse?
Make a plan, if possible. You can’t just kick your spouse out of the house (unless perhaps the home is titled in your name only), and leaving the house may impact your chances for obtaining custody or protecting property interests. Consider where you’re going, what possessions and vehicles you can take with you, who the children will stay with, how the children will be cared for, and how bills will be paid. If you can, discuss a separation with your spouse and agree on temporary arrangements. If possible, put any agreement in writing. A handwritten agreement signed by both parties is enforceable in court and will provide extra protection for you. If your spouse is not in agreement about a separation, consult an attorney before leaving the marital home. An attorney can assist you in planning for a separation that doesn’t jeopardize your rights.

How do I provide for myself and the children during the separation?
Once separated, you can apply to the court for several types of relief. First, you may request child support if you have custody of the minor children. The question is always "how much?" Both of you are going to have to contribute. One of you probably will think they are getting too little and the other probably will think they are paying too much. Fortunately, most states have implemented child support guidelines. This mandated method of calculation takes some of the guess work out of who pays how much.

But there’s more to support than a monthly check. What about education or braces or money for sports competitions? What about medical expenses or counseling?
The court can grant both temporary and permanent support. Be knowledgeable about how support is calculated; changing the amount of support is neither automatic nor easy. A modification of support in the future will require a significant change in financial circumstances. A second type of support is spousal support or family maintenance. You can request that your spouse contribute to the mortgage and household expenses. If the court has determined that you and the minor children should remain in the marital home, the court may also grant an award of support. The court will generally assess the needs of the party requesting relief and the ability of the other party to contribute.

How does a judge decide who will be awarded custody of the children?
The courts use the "best interests of the children" standard in assessing a custody situation. If the two of you can work together, then a joint or shared custody arrangement may be right for you and your children. If effective communication between yourself and your spouse is not a reality, sole custody may be the only option. Having the court decide who should have custody is the very last option. The courts also look to whether an individual’s bad acts are acts that have harmed the children.

What does "custody" mean, exactly?
Custody comes in two forms: legal and physical. Legal custody is the authority to make decisions concerning the minor child(ren)’s health, education and welfare. Physical custody pertains to where the child(ren) sleeps for the majority of the time. Generally, the courts will grant legal custody to the parent having physical custody. This makes sense since the parent taking care of the child(ren) may have to make emergency decisions. Two parents may share custody or one parent may have sole custody. There are several possible combinations of custody: shared (joint) legal with sole physical; shared legal with shared physical; or sole legal with sole physical. While many parents convey their desire for shared or joint custody, often courts are not inclined to grant shared custody unless that is the established arrangement.

SOURCE: DivorceNet