Types of fly casts:
Overhead Cast: The basic fly cast...
As I said earlier, this is the most basic cast in fly fishing and almost all other types of fly casts are based on the overhead cast. I also am not a fly casting instructor although I have taught dozens of others to cast. As I have said , I was taught by Mel Krieger and other great casters. I also am not a guy handy with video gear and organized presentations and I am not a writer. Happily, there are many others you and I can rely upon for these lessons and information. Most of this will be a collection of links to articles and videos I have read/watched by people much better qualified than I am...
I believe, as do many others, that the roll cast is the second most important cast to learn. The roll cast can be used in many situations. Off the top of my head, here are two: when there is no room behind you for a backcast and when the wind is coming from your back and interferes with your backcast. Also, the roll cast is very helpful in getting your line in the air to begin the overhead cast.
Note: "Presentation" casts - these are casts that will help you get your fly to the fish in a more natural manner...typically by reducing the potential for drag. The following five (5) casts are what I call "presentation" casts. They are the tuck cast, curve cast, reach cast, pile cast and slack line or serpentine cast. Some of these casts may have different names but the purpose is the same.
The tuck cast is very useful when you want to get your nymph or streamer deeper into the water column faster and leave behind some leader and tippet so you get a longer "drift". This one is pretty simple
The curve cast bends either to the right or left of you and is a "hybrid" of the standard overhead cast. Curve casts are used when casting the fly around objects on the surface or when you need to prevent the leader and fly line from "spooking" a fish as the fly passes over the fish.
The reach cast is very useful in many situations where you are casting across different currents and need to get a longer drag-free drift. You can also call it the "aerial mend cast"
The pile cast is very useful when you are above a fish. It really a "presentation" type cast. With this cast you "pile" up the end of the leader and tippet to get a longer drag free drift over your target.
Slack line or Serpentine Cast:
This is primarily a dry fly cast. It is also called a "wiggle" cast. Like several other cast, it puts slack line on the water and this gives you a longer drag free drift over a rising fish. It is very good when you have variable currents between you and the fish.This is a pretty easy cast to learn.
This cast is primarily a saltwater cast. You use it often when you are "sight" fishing for bonefish, tarpon and other species commonly found on the flats. If you have been there, it is often the case when you are standing on the bow of the boat looking for targets. Suddenly, the guide or another person in the boat says "tarpon at 10:00 o'clock". Many times, these fish on the flats are moving very quickly. Properly done, this cast allows you to make a 60-75 foot cast with just a few false casts. This is why they call it the "quick cast".
Double Haul Cast:
This cast is very useful in casting longer distances more quickly. This cast develops more line speed quickly and helps get your fly on the water sooner. The double haul is often used by fishermen that use shooting heads. Lefty Kreh is a "master caster" on top of being one of the great "characters" in fly fishing (first video). Lefty's take on the double haul is that it "puts more energy in the fly rod". In my mind, that equates to the same thing as increased line speed...make the rod do more of the work!
How To Double Haul - by Simon Gawesworth (Rio)
Tips and Tricks for a Better Double Haul - by Tim Rajeff (Gink and Gasoline)
Spey rods and spey casting have been around for quite a long time. They are said to have been developed in the 1800's in Scotland on the River Spey. They are a two-handed rod and exceptionally long and were evidently developed to make long cast for covering a lot of water (common in salmon and steelhead fishing). Another reason for their design was the fact that many of the Scottish salmon rivers are lined with trees and brush making a traditional backcast very difficult.
An Introduction to Spey Casting Techniques - video by Greys Fishing
A good article on all aspects of Spey casting - by Speydoctor.com
“Skagit” casting originated in the early 1990’s and it describes a hybrid adaptation of spey casting. Skagit casting was developed by US steelhead fishers on Washington's Skagit River. Many steelhead guys had started using spey rods in order to cover as much water as possible. But, in some rivers, the steelhead would hold in deeper and faster runs so the fly (very large flies) needed to get deep very fast. Skagit is really a marriage of more traditional shooting heads (usually sink-tip) with the long spey rod. Skagit casting has become popular enough that several fly line manufacturers have developed special "Skagit" lines to support this style of fly casting.
In some streams, low obstacles such as shrubs, tall grass and even boulders can present an obstacle in your backcast. When fishing in these areas it is important to have a high backcast that will unroll over the obstacles behind you so that you aren’t constantly fighting snags. The steeple cast was created specifically for beating these tough situations.
False Casting - False casting is simply the classic back and forth fly casting motion everyone has seen. It is necessary to false cast when fly fishing because we’re casting a long, weighted line instead of a simple weight, bait or lure as used in spin or bait casting. False casting allows us to change cast distance, change direction, and dry a wet fly. Learning how to false cast is an important step in the process of learning to cast.
Mending fly line - you may be a great fly caster...you may be able to put the dry fly wherever you want it to go. Good for you...but, if you cannot get that fly to float naturally into the fishes feeding lane, you are destined to limited success. Mending is a primary skill for a trout fisherman regardless of whether you are fishing with a dry fly or a nymph/wet fly. This is because feeding trout will almost always prefer to hold in a limited area when feeding. This is especially true when there are more bugs in/on the water. Most fish, especially trout are very aware of their environment and typically are most "comfortable" in places where they can find several things: food, safety and cover and, whenever possible, a current that does not require too much effort or it (the current) is "feeding" bugs down to them. Aside from helping to achieve a drag free drift, mending also keeps your fly on the water longer, thus increasing the likelihood of hooking a fish.