When it comes to fishing wet flies I concern myself with stream conditions. If the stream is high and has some deep pockets, I fish with an intermediate sinking line. If the water is medium to low I fish with a floating line. I fish exclusively with wet flies almost year round and always carry to reals with me, one with sinking line and one with floating line. When I get to the stream I scout and observe and see what conditions that I am going to face and then make my decision on which line to fish with. Now the type of wet fly fishing I do for the day is dictated by how confident I am in on which wet flies will work. If I am confident in the pattern I select and only fish one. If I am not sure at all then a three wet fly rig will be used until the Trout indicate which fly they like the best. Then at times I know that two patterns will work well and fish a two wet fly rig to see which pattern catches the most fish. You will hear alot of people talk about a wet fly swing which is great but don't forget to allow your fly line at the end of the swing to completely straighten out. Then hold the line for 30 to 40 seconds. I can not tell you how many strikes and Violent strikes that I have had by this method. Hope this helps you out a bit.
Sincerely
Andy Brasko