First off, I tend to avoid fishing for trout that you can see- they're usually spawning, stupid stockies that don't respond to normal fly fishing techniques, stressed (thermally etc) or otherwise uninterested in what I'm throwing. Anyway if I can see them clearly, its likely they can see me and are changing their behaviors accordingly. The best trout water usually has a little mystery to it- whether that be a shade line, increased depth, mottled bottom, murkiness, or distance and angle from you. I tend to ignore fish that I can clearly see (stealthily sipping fish notwithstanding- but thats a special kind of hunt anyway and probably more advanced than what you're trying to achieve now)
In order of increasing pain in the ***:
Change flies (shifting between confidence flies, increasing or decreasing weight, going smaller, trying duller more natural patterns and ones tied without beads), or maybe you do the opposite and put on something dumb, bright and ugly.
Change water type- Have you been fishing the runs and pools? try tightlining or running a dry dropper in the riffles, flip some rocks to see what kind of bugs are around and try to picture what stage a particular hatch is in. Sometimes the fish are in surprising spots. Learn to tightline nymph if you don't already know how to- its your best shot at unsuspecting fish all things being equal.
Change rig: if you're nymphing, try lengthening or shortening the distance between your two flies, or switch to a single fly, or a tractor trailer with a tiny midge, or add split shot and remove beaded patterns. Increase distance between dry and dropper if that's your technique du jour, do anything to try and mimic your best guess at whats going on in the water. Fish aren't that smart, they're just opportunistic and don't like to break their routine.
Change tactics- try a streamer especially if its colder and lower light, try a strike indicator if you've been tightline nymphing, I don't usually waste time with dries unless there's a hatch on but I suppose you could prospect with one of those too if all else fails
Change location entirely- some rivers are just tough, or there are no bugs in a particular section so I won't spend too much time there if it feels off (looking at you- Delaware). I'll often bail after a half-day of slow action on certain rivers that I know are feast or famine to go hit up another local waterway that has easier pickins. Time is money afterall.
Don't try too hard, fishing is best done confidently and from a relaxed perspective. Remember it could be worse, you could be at work.
