I know it depends - season, weather, day time, what else? How do you choose a fly? I almost always fish with two guys, same boat, same lake. And once we'd been using same flies for almost one week. Exactly same flies bought in same store at same time. The luck each of us had yet was quite different. So not everything depends on a fly you use, lot's depends on your skills and how you wield the rod. absolutely agree. you can use same fly in lots of ways - wet, dry, flyfishing, rigging also matters see what is flying above the water and use the most similar one you have there can be all sorts of flying midge, you should know what fish is after