As the others have said just make sure you get something comfy that fits your foot, don't bother with getting a cripplingly tight pair like *some people* suggest, it's a waste of time to begin with and will just put you off as your feet will hurt so much. As long as they fit they don't need to be cutting of the circulation, save that for your next pair.
Oh, and try lots of different makes on, just becasue one brand doesn't fit you doesn't mean they'll all be the same, I can't get my feet into a pair of 5.10s but loads of people swear by them, you have to try them all on to see what suits the shape of your feet.