[quote name='anotherjeff']ebay, half, amazon, and gamefly are usually good choices as long as your willing to thoroughly read descriptions of items.[/quote]
Yes, always read all the descriptions of the items on ebay and if they dont explicitly state the game is complete and scratch free, just send a quick note asking them to verify that it is.
I'm not saying you will never get a game that is oversold as "MINT" when it clearly isn't, but you definitely improve your chances of getting better quality items by doing that little bit of due dilligence.