1st rule of bounty hunting.
If they know you are looking for them, you are not going to find them, so stay as low key as possible and try not to attract too much attention to yourself. For example.. dont publicize the fact you are a bounty hunter.
2nd. Join IRC, join large public channels and see who talks. See if any of them have bounties and if they do, perhaps listen to what they say to find out where they work, where they are, what the like, etc.
You are extremely unlikely to just happen across anyone you are looking for in the depths of space without tracking them first.
Also... you need to have have the proper privileges to arrest someone. Contrary to real life, you cant just walk up to someone here and put them in handcuffs. Also you cant just knock on someones ship and let yourself in. If they want to stay inside and are smart (especially if they know who you are or why you are there), you are not getting in.
Thats a start.