Just a quick guide based on my experience here on eBay.  I have bought numerous nba ( 1 NFL) tickets throughout the years and have nothing but good luck.  I am sure to check on feedback and rarely bid on tickets where sellers don't disclose how they will ship.  Sellers, it is better to include lots of information in the auction even if some buyers still don't read the auction details and hound you with questions.  I have had two sellers first class mail me very expensive tickets with no tracking.  A huge no- no, what were they thinking with no way of tracking them, a seller puts him/herself at risk.  Always pay via paypal with a credit card, you have protection this way.  If you don't get your tickets you can do a chargeback but be sure to check with the seller to try and settle your differences first.