I set a couple marks out here on the lake then time myself to see how long it takes me to do one lap. Then do it again, changing a few things, then again, etc. until I've got it down to the lowest time, but the wind on a lake is never really consistant enough to know if I'm getting better (or worse) or if the wind just shifted or blew harder, and made me faster! But it does teach you to always be looking for the next puff, both upwind and down.