A mayfly dun with fish rising points at a dry fly such as a Parachute Adams. The same insect as a nymph, with no rises, points under the surface. A sipping fish wants a smaller emerger or spinner and a lighter tippet. A splashy rise on a caddis evening points at an Elk Hair Caddis.
Water changes the hook
Spring creeks and tailwaters step the hook smaller. Wind steps a dry fly larger so you can still see it. Cold water, under about 48 F, keeps the day on nymphs unless the insect is a midge. Warm late summer, especially with no hatch in the air, moves the box toward beetles and hoppers.
The top fly is free. $5 adds four more flies, the rig, the tippet, a backup from a different rig, and a printable checklist. If you are not fishing a fly rod, Lure Picker covers spinning and baitcasting.
Fly Picker matches a hatch from the insects and the water you describe. It does not promise a fish, and it is not a substitute for local regulations. Check seasons, access, and tackle rules before you fish.