Doing these a fair bit at work, there are a few parts. First is service. If you are in a last known address jurisdiction, registered mail to his last known address is often enough to proceed. He could have it overturned by motion claiming he was never served, but that would require him to stick his head up, and that will give you the new location. The court may overturn the judgement, but will not toss out a case for incorrect service. Every jurisdiction is different however, so check yours.
The second is obtaining a judgement. This will cost between 50 and 500 dollars depending again on the fees of the local courts. Easy enough to obtain, it's mainly a paperwork and money exercise where he does not defend.
Finally, and this is the hardest part, you have enforcement. Even if you get a judgement, the court does not enforce for you. You need to find his assets and serve your judgement against. If it's out of your jurisdiction, it can be a nightmare. Of course, if you have judgement, it shows on their credit record even if you can't enforce (at least here it does). Makes loans, apartments and in some areas employment etc harder to obtain.You may get nothing but the satisfaction that the guy is going to get hassled for several years. Of course, if he has a bank account and wrote you a cheque, you can try to garnish the account...that assumes he has something there, and every enforcement you commission will cost you money whether they find anything recoverable or not.
In general, if you can't trace the guy cost effectively, it's often cheaper to just let it go until you can find him. It sucks, but the civil courts are only there to give you the tools to make things right...they don't actually do anything in and of themselves to make it right.
