Hmmm, the best one is by taking an expensive item and putting it in your 'Junk stash'. Then go to a merchant and go to where your junk is and hit Y then VERY quickly his A. Y sells all junk and A sells selected item. If you do it right you'll sell the item twice. Then you can buy it back and keep half the money.
Gamertag- woodsc21 Awaiting - Mass Effect 2, Assassin's Creed 2, Modern Warfare 2, Alpha Protocol, New Stone Sour CD, Next Stone Sour Tour