I looked at lots of fly rod reviews and my favorite rod is a St. Croix, Avid, 8'6" 4 weight, 2 piece. When talking about fly rods the first thing to look for is the name of the manufacturer and what series the rod is. From there you should check the length of the rod, the line weight and how many pieces it breaks into. The rod I have is made by St.Croix, from the Avid series. It is an 8 foot 6 inch long rod (8' 6"). This rod is made for a 4 weight (4wt) line and breaks down into two pieces 4' 3" long.
When choosing a fly rod you want think about the average size of the rivers you will be fishing. The longer the rod the easier it is to control the line once it is on the water. If you are fishing a small, tree lined creek then a 9 foot rod might be hard to cast under the trees. If you look online there are a lot of fly rod reviews for different lengths and weights.
The weight of a rod depends on what size of fish you will be catching, how far you need to cast and how windy the area is. A 2 weight rod is a lot of fun to catch small fish on but will be difficult to cast in the wind. The most common rod is a 9'- 5 weight which can be used for all types of fishing. If you are only going to buy one rod this is the size I would recommend to learn the fly fishing basics. For a first rod combo I think the Temple Fork Outfitters NXT rods makes the best starter kit for the price.
A fly rod can be made out of several different materials. Early rods started off made of bamboo, then went to fiberglass and now are mostly made of graphite. Companies have also introduced Boron and a high heat resin into the mix to make rods lighter and stronger. This adds considerable cost and at this point it will be hard to tell the difference if you are still learning. When talking about graphite rods manufactures grade the quality of the rod in modules. Here is a rating chart on how graphite is measured.
IM-6 Graphite = 30+ Ton Material (Standard Modulus)
IM-7 Graphite = 35+ Ton Material (Intermediate Modulus)
IM-8 Graphite = 40+ Ton Material (Intermediate/High Modulus)
IM-10 Graphite = 54+ Ton Material (High Modulus)
In the last fly rod review I read it did not give the module count for the rods.
Tip Top and Snake guides:
This is the topmost guide at the smallest end of the rod and the easiest to break. The snake guides are the next several guides, between three and seven, depending on the length of the rod. The guides need to be evenly spaced to distribute the weight along the rod when fighting a fish. Always look at the wrapping on the guides which secure it on the rod. Make sure they are evenly wrapped and have a hard, epoxy coating.
These guides are closest to the handle and allow the line to flow freely down the rod. Guides are made of nickel, silver, anodized aluminum or other metals which will make them lighter and more durable but can also make them more expensive. One of the most expensive is the Recoil guide which retains its shape even if bent.
There are several different shapes of handles and this is where you have more choices. Get a rod that feels good in your hand, something you can use all day long. You can look at some of the fly fishing magazines and fly rod reviews to get a better picture of the different handles.
The seat can be as simple as two sliding rings on a cork handle. The bigger the fish the more secure the reel needs to sit on the rod. Heavy fly rods have a screw closed seat and a second ring to lock it in place. If you have a rod custom made or want to pay more money you can have wood in the seat with silver or gold as the metal.
Orvis Trout Bum is a good example of a rod with all the trimmings which retails for $575.
As you continue into the world of fly fishing you will gain a better understanding of the gear you like. I try to pay less for my rods so I can buy more flies. You may like the feel of a nicer rod to make the experience more indulgent. It is all up to you. Just make sure to read some fly rod reviews before heading to the shop, that way you do not walk out spending more then you wanted to.