I usually base what I use around the time of the year and the size of the water. When its cold, beadhead nymphs, soft hackles, and streamers. During the main part of trout season such as now, I'm usually 95% dries, but if the water is larger I like to use the dropper rig that Dude mentioned.
Maybe I've just grown impatient, but whenever I get a knot in one now, if it looks like it'll take longer than 2 min to untangle, I bite it off and re-tie the tippet and rig.
1. He said small class A streams. I wouldn't advise it on a small stream unless you enjoy frustration.
2. Too many trout get foul hooked. That is not a slam on anyone. It is just one of my reasons why I rarely use them on wild trout.
3. The small stream wild trout are not very selective. As long as you don't spook them, you can usually catch them. Start with a single fly. No need to add a dropper from the get go. Then if you are not having good success, go ahead and add one.
It depends on conditions, I usually start with dries, and choose flies that should be hatching. I they don't work, then I try either nymphs, which I hate fishing, or streamers.
Since I've stopped doing tandem rigs on small streams, I've been a lot less fustrated. You get a better drift with a single dry. When I really want to work a hole, I'll give the fish a break while I tie on a single nymph without an indicator or wet fly. Swinging a wet or a streamer is the best way to fish in front of a log jam IMO.
My go to fly on small trout streams is small ant. Works on just about any stream and almost anytime of year. I've seen piles of ants even in late nov. I always start with a dry fly of some sort but if I don't see any results its back to the ant.