Always contact or visit the local fly shop to find out what’s hatching, what flies are working and where. Also check flow conditions and temperature.
As I mentioned in another thread, try fishing your flies downstream (and wade downstream – it’s easier)
Move to fish different water types and different sections. It’s amazing how many times nothing’s happening in one spot, and the fish are going crazy on another part of the river not far away. When I fish with a buddy, I bring walkie talkies. We usually split up, and cover different water. When someone finds fish, a hatch, or a fly pattern that’s working we call each other. If nothing is happening, we call to meet up and move to another spot.
Prospecting with a dry fly when nothing is rising is a low percentage way to fish on big water. Also fishing with tiny flies is tough, unless you are matching the hatch to active fish. Buggers, big stonefly nymphs, larger GRHE, etc. are all good prospecting flies.
Use streamers to cover a lot of water when searching. If you have follows or short strikes you’ve found active fish. Slow down and fish the area more thoroughly with nymphs or other flies. The most versatile searching fly for me is a wooly bugger. I often fish it like a nymph (dead drifted) and let it swing in the current at the end of the drift, then I strip it back all in one cast, to find out what the fish prefer.
Sink that nymph. Don’t be happy until you begin losing a few flies. Sometimes in faster deeper water using a lot of weight, a strike indicator is a liability. You may want to try highlights spaced out on your leader (strike putty works) and/or a hot butt leader to follow by sight. Also get to the bottom and use your sense of feel to detect the bottom and strikes.
Reading the water to find the prime spots is important. Current seams, behind and in front of obstacles, heads and tails of pools, etc. If you catch fish in one type of water, seek similar areas to fish.
When you do see rises, take your time and try to capture a few insects to match. Many times there is more than one type of insect on the water. Try to determine what they are feeding on. I usually start with an emerger tied behind a visible dry fly. Cover the fish with a some good drifts. No takes, change patterns or type of fly. Don’t just pound the rising fish with every dry fly pattern you have. Often the best way to catch rising fish is with a fly in the film or well below the surface. Don’t forget about soft hackles and caddis pupa flies.
Fish early and late. I can’t tell you the number of times I fished during the day and swore there were no fish in the river, and the last hour all hell breaks loose. Most of my fish are usually caught near dawn and dusk, especially in the summer. You may get some good hatches midday early in the season or on cloudy/rainy day but in the bright sun during the summer midday is a good time for a nap.