Anglers often forget that a trout’s eyes are on the sides of its head and not pointing forward, like human eyes. Thus, the fish’s peripheral vision is far more effective than ours is. And yet, when we see a fish laid up or sipping in calm clear water, we always try to sneak in for that cast from the side. When we get just about close enough… poof, the fish darts away and we wonder why.
When fishing in calm water the most important tip is to keep a low profile. The number one factor that spooks fish is shadows, when they detect motion in their vicinity. I cast from my knees—and from the bank—as often as possible. I keep my boots as dry as possible, because even the smallest wakes and waves will put feeding trout down. I try to position my body so that my shadows (and the shadow of my fly rod) are not cast directly over the target. Never false cast directly over the target fish.