I will usually try and find a spot that has several choices to fish (pool, eddy, riffle, structure, etc) and i will cast to each spot several times, and if the hits are spotty or not there at all, I will move. One of the big things I learned is to not just get out of your car and jump in the water (unless you are fishing at snaglet #2 I tend to watch the water for a couple of minutes, see what the fish are doing (surface feeding, no rises, etc) and try to get a look into the water and see where they are stacked up. Then I make my decision on what fly to use and go from there.