In fishing terms the streams are not difficult to fly fish, assuming you are physically fit enough to follow the stream for a long route with obstacles, climbing rocks along the shore and finding your way in the forest. The trout will often respond eagerly taking nymphs, wets and dries. The streams are not rich in food, especialy at higher elevations. On the small freestone streams there is a wide variety of different insect forms - Caddisflies, Ephemeroptera, Stoneflies, Diptera, terrestrials etc., but in a much lesser numbers than in a rich food source water such as a spring creek/chalkstream.
The scarce food and the harsh conditions force the small stream (/freestone) trout to take our flies in less discriminative manner, rewarding both the novice fly angler and the old gun although in a different ways. Over here a newcomer to the sport of fly fishing may start with the chub, but the next level to the brown trout may be the small stream trout. Fly fishing the small streams is a good way for the novice to build confidence in flies, methods and presentations. In my observations the hardest part is often not learning how to cast, but building confidence in your arsenal of fly fishing tricks that
will only come with practice. As for the old gun - the reward of fishing the small stream is always there - by just being on the water fly fishing!
Here is some of the stuff I use on small streams:
Nymphs - 8-18 - bright and dark hare's ear nymphs with variants
Wets - Gary LaFontain's Diving caddis and variants
Caddisflies - Gary LaFontain's Deep Sparkle Pupa and Sparkle Pupa
Dry fly and Emerger - Comparaduns, F fly, some English traditional patterns and variants