You can try e-mail, Google, or asking people like parents and former neighbors who knew your friend. A letter mailed to the old address might be forwarded.
The internet is an amazing resource. If you have some pretty basic information it should be pretty easy to do a goggle search. Or you could contact family and friends.
Using a search engine to find their name might help. Do you know anybody else who knew them to ask? If all else fails, hire a private detective. They have more resources available to them.
