What shouldn't you do when camping?
Post your biggest mistakes that you've personally made.
One camp I made a few errors:
I should have positioned my tent so the ends were facing the way the winds could come from. It was in a Scottish loch valley with mountains either side so there were only 2 directions for it to come, but I wanted a better view. 
I shouldn't have put my tent on a bit of land sticking out into the loch where the wind would get me.
I should have paid more attention to the weather forecast and given up when told the wind would be 55-60 mph gusts.