Re: general flyfishing question...
Well, There are several different methods but generally speaking, if you fish dries upstream you will mend the line i.e. throw slack or throw line downstream in an arch in order to avoid drag on the fly.When the fly comes down towards you in upstream dry fly fishing you begin to take home line so you will have line control in case a fish takes and also so you will be able to throw your line in a new cast instead of having to do a lot of false casting. If you fish downstream with dries you have to constantly throw slack and or mend in order to avoid drag. Remember if you have drag on the fly, i.e. if the fly is skittering you won't catch anything 98% of the time. There are exceptions but they are rare. If you are nymphing you would do the same if you nymph upstream. If you are nymphing downstream with the old wet fly techniques you would slowly take home line as you let the nymph come float downstream to avoid drag. When the nymph comes to the end of the drift you can start slowly taking it home and you will probably get a strike if you didn't get one on the swing at the end. Hope this makes sense. If you are fishing close and are using what we call high sticking you basically only use the leader and maybe a foot or two of line. You are holding the rod high and following the line as it drifts downstream. Be ready for a quick strike and lift your rod immediately. These are some ways to fly fish others can tell you about more advanced techniques such as shooting the line and double haul.