Fly fishing beginners often work their way downstream, using either a dry or a wet type fly. Understandable, since it's easier to walk with the stream than against it. Casts are ninety degrees off to the side and then we let the fly swing downstream. You should note that with this method your line will form a loop between you and the fly as it drifts, so try to flip that loop back upstream. When a fish takes your dry fly this way it opens his mouth and lets the fly drop in. But the fly doesn’t want to go as it’s hooked to your leader and doesn’t drop as fast as he’s used to. By now though, the fish has closed his mouth and turned down, and you’ve have missed it. Either that, or the fish has missed your fly.
You’ll have more success hooking by casting upstream. As the fly floats back a fish takes it, which holds true whether fishing wet or dry. In this way the chances of hooking a fish in the corner of the mouth (the best place) is far greater. Commonly, fish hooked downstream will only be caught in the front of the mouth or lip, neither of these places being as secure as the corner. The fish will have a far better chance of escaping when hooked that way.
Hooking in lakes is an altogether different matter. If the fly is dead and drifting on the surface, tighten your line as soon as you see a splash. By making it tight just by pulling on the line rather than lifting the rod, you will hopefully prevent ripping the fly away from the fish in case he misses. If you are fishing deep, though, it’s not a problem, as you will feel the fish.
Finally, remember to sharpen your hooks and keep them sharp, and check the point often, as snagging on trees or rocks can do damage. So there you have it, a few useful hooking tips for fly fishing.