Write your contact information on a piece of paper.
PUT IT IN YOUR WALLET.
Make sure it's somewhere prominent.
For the second time in a year, I found a wallet but couldn't easily contact its owner. It looked like he was a mechanic at LAX who regularly rode the FlyAway bus from Union Station, and he could have had all those very official IDs back right away if he'd just left a phone number. As it is, I wasted half an hour getting it to a Lost and Found he may never check. With Amtrak and Metro and FlyAway all right there, I didn't know where to start, and for once security guards were scarce. I ended up leaving it with Amtrak, since they seemed to be the biggest presence at the station, but I also left a note with FlyAway because I thought he might check there first. They probably thought I was crazy. But I tried.
I lost my wallet in the closing hours of Comic-Con a couple of years ago, and thoroughly freaked out. That had a happy ending, but I still didn't put my phone number in my wallet. Until now.