Legal separation can be difficult to understand because the same process isn't recognized in all states. In some jurisdictions, you must simply sign an agreement with your spouse to become officially separated. In others, you must involve the court. Universally, however, a legal separation defines the terms of living apart. The differences lie in how you achieve this.
In some states, such as Ohio, you can file a complaint for legal separation just as you would file a complaint for divorce. This requires grounds. You can ask the court to decide issues of property, support and custody. After you file, the litigation typically proceeds through the same channels as a divorce, with temporary orders governing until a final decree is issued, an exchange of information through discovery methods such as interrogatories or depositions, and a trial after which the court makes a ruling. Just as with divorce, you and your spouse can reach an agreement on all issues at any time and submit it to the court for approval rather than go to trial. In either case, the court issues a decree of separation. Its terms are binding. Either you or your spouse can go back to family court at any time to enforce them if one of you doesn't abide by the decree's provisions.
Among states that provide for legal separation by court order, the process sometimes goes by different names. For example, in Maryland, you can get a limited divorce. In New Jersey, you can get a divorce from bed and board. The procedure is virtually identical to what's required in states that allow you to file a complaint or petition for legal separation. These processes also move forward much the same as a divorce. You can't remarry, because technically, you're still legally married to your spouse. But the court can address all other issues at trial, or you can submit a settlement agreement to avoid trial.
Separating by Agreement
In states that don't recognize a judicial separation process, you can legally separate by agreement with your spouse. This involves negotiating a settlement on all issues, or even just a few issues. For example, you might elect to live separately and apart but not divorce just yet, and the only issues you're really concerned about are custody terms and child support. You can write these terms in an agreement, and when you sign the agreement, it becomes a legally-binding contract. You can also divide property, assign responsibility for debts, and provide for spousal support. The agreement will govern your separation indefinitely if you never decide to divorce. If either of you break it, you would typically have to enforce it in civil court, not family court.
Conversion to Divorce
If you ultimately decide that you want to end your marriage entirely, the requirements for doing so vary by state. If you're happy with the terms of your legal separation, you can often carry them over into a final decree or judgment of divorce with very little fuss. For example, in Ohio, you can petition the court to convert your separation to a divorce. In New Jersey, you can include terms in your judgment for a divorce from bed and board, setting a specific date or certain circumstances under which your marriage will legally and entirely end. In Virginia, you must file for divorce, but you can ask the court to incorporate your separation agreement into your decree.