In many ways [the approach] is simple: Don’t scare the fish before you cast to them. A scared fish is no longer a candidate for a hero photograph, or, as my friend Bob Scammell so succinctly put it, “Nobody’s good enough to catch a terrified trout.”
While the fish in heavily fished waters are usually more tolerant of an angler’s presence, you can still put them off their feeding by getting too close, by sending a wading wake out to alert them, by making sloppy deliveries too close to them, or by false casting over them when they’re in shallow water or near the surface. So watch awhile first before barging in and starting to cast. Look the situation over. Are the fish rising? If so, to what? Look at the water near you and try to see what bugs are on the surface. If you don’t see anything right at the surface, try to find out what’s drifting just beneath the surface (a small aquarium net or piece of screen makes this easier). All this will give you an idea of what fly to start with.
Jim McLennan, Managing Editor