Good luck, they were just some ideas to save a couple bucks before hiring someone and paying a lot more. That's why I suggest a public records search, not only will it hit the tax records, it will kick back his drivers license, cars, court records, and stuff based off his credit report for addresses (but not his credit rating). It's not hard stuff, just takes some time and leg work.
Edited to add: If your friend has a big enough lawsuit/claim, often the attorney will hire someone to find the guy, provided your friend has enough information to track him down (name, age/dob, maybe SSN if you're lucky. If your friend has canceled checks he wrote the guy, there should be banking info on the back, when they were cashed. An attorney could get a subpoena or court order for the bank records, which is another way to find him and it also can show other stuff he might have been up to with regard to fraudulent practices).