In the case of folders, a lot of people think it's better to wind before the shot than after, because opening the camera from the folded position can create a vacuum effect and pull the film away from the pressure plate. Winding on should take up any slack and give you flatter film. I don't know how significant this effect is in the real world, especially since folders aren't that great at film flatness anyway.

The main thing is just to have a consistent routine. Even so, with any camera that doesn't have an interlock between winding and cocking, it just seems to be a law of nature that double exposures happen occasionally.

-NT