The first knot that will be used when rigging up a fly rod is one for attaching the fly line backing to the reel. This knot is known as the Arbor Knot, and basically involves wrapping the backing around the reel twice, tying two overhand knots, and then sliding the knots down onto the reel spool face. This knot needs to be tied very securely, because if a big fish takes you all the way to this point in your backing and the knot fails, you don't just lose a fish, but also your fly, leader, and all your fly line and backing. Proper tying instructions or all the knots referred to in this article are available in the Resources section.
Fly Line to Backing Knots
The knot to connect the fly line to the backing is the first in a series of knots that needs to have a low profile and smooth surface so that it can go through the line guides easily, without getting hung up and causing you to break off a fish. Most fly fisherman choose to use the Albright Knot or the Nail Knot for this connection because they offer these characteristics as well as a good way of joining two lines of different diameters.
Line to Leader Knots and Loops
The aforementioned Nail Knot and a similar knot known as the Blood Knot are also used for the fly line to leader connection because those two lines have such differences in diameter, but many times fisherman will want to use some sort of loop knot here to make it easier to make quick changes to the rigging. The loop knots that are best in this situation are the Surgeon's Loop, Perfection Loop, or some even choose to use a loop on both ends with a loop to loop connection.
Knots for Adding Tippet Material
In the course of fishing, you will inevitably break off or change flies, losing a little bit of your tippet each time. To add tippet material, you will want to utilize knots that are effective in joining two lines similar in diameter. The Double Surgeon's Knot or Triple Surgeon's Knot fit these criteria nicely and are easy to tie.
Tying on the Fly
There are two knots most commonly used for tying the fly to the tippet; the Clinch Knot and an evolution of it called the Improved Clinch Knot. For those applications where the fisherman wants the fly to have freedom of movement, a looped knot, such as the Duncan Loop, is used. Take care to use the right knot for the job and you will improve your chances of landing that fish you have worked so hard to hook.