Lately, I see many people giving the advice to place a mainboard on the anti-static bag it came in to test the setup.DON'T EVER DO THAT! STAY AWAY FROM THOSE BAGS, THEY ARE OF CONDUCTIONG MATERIALS!!
Have a look here: http://en.wikipedia.org/wiki/Antistatic_bag
There are people who's board burnt out completely with the bag melted to it, after testing on an anti-static bag.
If you want to place your board outside a pc-case for testing, lay it on a piece of cardboard with no print on it. Or use another surface of which you are 100% sure it's non-conducting.