Here's a trick I use: most PC ports have the flat plastic (inside) on the top half [0], I have noticed. So, if you look at the USB dongle/stick/cord it will have some small holes punched in either flat side usually. Just look for the holes that aren't blocked by the flat plastic part [1] and make sure those are up, then you should get 95 percent of them correct.

[0] http://i.imgur.com/k09dgzL.png [1] http://i.imgur.com/6sChr0E.png