Carp are big fish, much bigger than the trout most are used to catching on a fly rod. Because of this, having the right equipment is paramount in having a successful carp fishing trip.
The best fly rod to use for carp is a 7-9 weight with a fighting butt of some sort. Fishermen will need every bit of leverage possible to work in the fish. The larger rod also has more backbone for casting larger flies. If a person plans to use a smaller rod, make sure to let the fish run with the tip pointed toward the fish, and be careful when cranking in the carp. They will often turn suddenly and make violent runs that can snap a rod like it is a matchstick.
A good reel is also important. Make sure that the reel has a good drag system and can hold plenty of backing. It is very important to make sure the knot between the fly line and backing is secure. Undoubtedly, many of the carp hooked will test the knot, and possibly the amount of backing on the reel.
As for line, a good floating, weight forward line will work well under most conditions. Leaders should be about a rod's length long. A 6 to 8 pound tippet will work if fisherman are careful. Remember that carp have a sensitive mouth and can often tell when something is not right. However, they are also quite large and can trash smaller tippets with the shake of a head.
Probably the most important thing in successfully landing a carp is a net which needs to be large enough to scoop up the fish.They are not like a trout that can be picked up out of the water by hand. There is no real good place to grab them. Trying to land a carp without a net is like trying to pick up greased watermelon.
Really, fishing for carp is not much different than fishing for any other species chased by fly fisherman. Just keep in mind that the fish are big and will test any equipment no matter how tough it is.