When moving try to stick to long lines of sight so you can see any other players coming up. If its a large map try to flank their position if possible, try to avoid going up the middle of the map as you would be easily overwhelmed if the other team get around you. If it's a small map find 3-4 positions where you can see a large part of the map but are well protected (limited chance of being flanked etc), and wait to pick one or two of them off, then revolve your position, if at all possible you don't want to camp; not only is it annoying but after a couple of kills the other team will know where you are. If you're able to, revolve your next position with a line of sight of your previous, that way when the other team come looking for you at the previous position you can pick them off once more.
I find this works; hope it helps.