Money order or cashier's check. Or cash (somehow). Or Western Union.
Paypal has a default take-the-buyer's side in a dispute that could screw you -- never happened to me, but there are plenty of Ebay sellers who have been screwed this way.
I imagine a bank-to-bank transfer would work as well -- I've done it paying for things, and had people transfer to me, but I'm just not sure what would happen if there was a dispute.
And, obviously, no checks.
If they do a money order or cashier's check, you can also tell them they have to wait a reasonable amount of time before it clears -- or go to the bank at which it is drawn and cash it immediately. Some people try to scam with fake cashier's checks but they are usually pretty suspect looking.
If it's someone out of state and you tell them you want the check to clear or you need to be able to cash the check before you ship, if they balk at that reasonable request then that should raise some flags. And, overall, trust your gut. I've done some deals where I just kind of had the intuition that it was right ( recently broke a rule and took a personal check for some work, but the guy seemed nice and genuine and no trouble cashing the check a few days later).
