I used to put my full name, PDGA number and phone number on there. I've only gotten one call back, and it was on a disc I lost in Colorado Springs. The guy had already driven back to Denver, so I just told him to keep it. Still a nice gesture though.
Now I just use my initials and PDGA number, and that's just to meet PDGA rules about marking discs. I have lots of discs, so losing one doesn't bother me too much. Sometimes I will ink something wry and witty. Like my Pumclops DX Roc3 says "Put that thing back where it came from or so help me..." on the rim, in reference to Mike Wizowski of Monsters, Inc. I have a used 11x Champ Firechicken that no longer has a stamp, so I signed "Big Country, 0x Disc Golf World Champion" on the front.