i use paypal already.  how do i go about selling credits?

There's a thread in the Book Bazaar called Looking to Buy or Sell credits where you can post how many you have to sell and how much you want. I posted there the other day and I also put a note in my signature. I sold 20 today to someone who saw it in my signature line. She PM'd me with how many she wants. I pm'd her with my Paypal email address. When she sent the money, I buddied her the credits.

If you are comfortable with other forms of payment, be sure to mention it.  I've sold credits and took a personal check, and it worked just fine.  Not trying to convince you, just make sure to list whatever forms of payment you will accept.

Make sure you know what kind of Paypal account you have--can you accept credit card payments or does it have to be bank transfer or Paypal balance transfer?  If you can't accept CC payments, definitely specify that.

Usually the procedure is the other person PayPal's you the money (or sends a check) and once you have the money in your PP account you buddy them the credits.

http://www.paperbackswap.com/forum/topic.php?t=147585  is the current thread in the book bazaar.