When you are fly fishing the hook that you put at the end of your line is absolutely critical. Knowing what the trout you are targeting are feeding on, or will strike at out of anger will allow you to pick from the thousands of variations on fly fishing flies.
Choosing the right flies to use can be a daunting task for a new fly fisherman, but luckily they are broken down into these three main categories.
The classic dry fly is what most people think of when they picture fly fishing. These are exactly what the name implies, and are lures meant to imitate bugs landing or skimming across the surface of the water. Because of this, extra care needs to be given to matching what insects are on the water when you are fishing aka. Matching the Hatch.
As the name implies, wet flies are types of fishing flies that resemble insects that are under the water. This includes dead insects and insects that come up and emerge from the water. These flies can imitate everything from small water bugs that are nearly invisible to things the size of Crayfish.
A streamer is a class of wet fly that is meant to look like an injured baitfish. Typically streamers are used to target larger fish as trout over 12" tend to start shifting in exclusively feeding on other fish.
Nymphs are the immature bugs that have hatched in the river. After they emerge from their eggs they migrate to the surface and there they become a fly. These type of fly fishing flies uses different forms of nymphs that are weighted down to remain beneath the surface.
These fly fishing flies can be used as wet or dry flies. They are made to look like larger insects that mistakenly jump or fall into the water and drown. They can also be made to look like an insect trying desperately to free itself from the water or as an insect that has already died and is simply sinking into the water without movement.
Choosing the right fly to use.
As mentioned before, your greatest success in fly fishing will come by matching the hatch, meaning that you use flies that match what the trout you are targeting are actively feeding on. This takes some practice as well as spending time on the water and looking around at what bugs you are seeing out. It does take time to master, but it is well worth the effort.