There are two issues surrounding where a case will be filed - jurisdiction and venue. There is a course in law school dedicated almost entirely to these issues (civil procedure), so unfortunately I can't give a comprehensive answer to the question that suits every situation. The general rule is that cases must be filed in the state and county where the person you're filing against lives, but divorce and family law have more exceptions to that rule than probably any other area of law. 

Filing your case in the wrong state or county is a costly and time consuming mistake. In some instances, you'll need to file in the state or county of your spouse or ex spouse. In others, the case must be brought in your county of residence. Where the case will be also depends on which person files and which person doesn't. If you need to know where your case needs to be filed, the only way to be sure is to speak to a qualified attorney about the specifics of your situation. If you'd like to discuss those specifics to find out where your case should be filed, call The Lilly Law Firm today at (678) 807-9150.