In theory, fly-fishing is a simple sport: Pick a body of water, choose a fly-fishing rod, select your “fly” (or bait), tie a secure knot, cast your line and, hopefully, land a fish on the other end.

Fly fishing for trout can be one of the most rewarding and exciting outdoor pursuits there is. It can also be one of the most frustrating. I often hear people who don’t fly fish talk about how ...