PayPal only. It just makes things easier and safer for both parties.
Shipping information
Books usually go media mail, other goes priority unless requested for different shipping method.
Return policy
I sell the kind of stuff that doesn't usually ask to ever get returned. In fact, I have never had one return request in my entire time at eBay. If the circumstances were right, and it was a problem wasn't with the shipping company or the buyer, I'm an honest guy and would do what it would take to fix something I did wrong.