My best tip to finding the right fly, especially if you are nymphing, is to seine the water before you start fishing. Spend $3.97 for a two-pack of five-gallon paint strainers at Home Depot, which will fit right over a net. Get a buddy to stir up rocks and river bottom a few feet upstream while you you stand downstream to catch all of the stirred-up bugs floating downstream.
After 15 to 20 seconds, you should find an assortment of the aquatic life in the particular river. And, you never now what you’ll find … leeches, big, beautiful stoneflies, mayflies, midges, etc. You’ll quickly be able to key in on the type of bug, color, size and life stage, which will significantly improve your probability of a successful day out on the water.
— Joe Newsum