Fly lines range in overall length between 75 and 150 feet and are made to either float or sink. A sinking line can be full- slow sinking, full- fast sinking or just sinking tip. One instance for using a sinking line would be lake fishing or fishing in very deep holes in a stream. Since you can achieve the same sinking effect with weights added to a floating line’s leader, that’s the one I recommend for your first. The floating line provides the best results in almost all cases.
Let’s now look at the various line designs. There are three main types; 1. The level line, 2. The double taper (designated by initials DT), and 3. The weight forward (WF). As its name implies, the level line has the same diameter for its entire length, while the double taper narrows at about the length of 12 feet at each end. The weight forward has a larger diameter for about a third of the front end before tapering to the tip. For your first fly line I recommend the weight forward line because of its ease of casting.
Now let’s talk about backing and why you need it. Because of the way that reels are designed, fly line alone would not fill the spool. So, one reason for backing is to provide a base for the fly line. Another reason has to do with what happens when you encounter a long hard run by a larger fish such as a steelhead. Since it is possible for such a fish to pull all of the fly line out of the spool, it’s a matter of necessity to have extra line in the form of backing.
Backing line is for the most part made of Dacron that doesn’t rot or weaken when wet. Its length and strength depends on the weight of the fly line. For fly lines from 2 to 4 pound weight the average backing would be 50 yards long and 20 pound test. Fly lines between 5 and 8 pound weight could call for 80 to 150 yards of 30 pound test. You would need up to 300 yards of high quality Gel Spun (smaller diameter with higher strength) backing for fly lines of 11 to 12 pound weight. Such lines are mainly used for big game fish such as Tarpon, Salmon, Strippers and yes even sharks.