How To Choose Surfboard Fins

There are many types of surfboard fin systems to choose from. Choosing the one that you want is an important part of choosing your surfboard. Fin characteristics as well as the brand of fin system are to be considered.

Most surfboards today come with the removable, as opposed to glassed-in, type of fin. Most brands do not have cross compatible boxes. Boxes are the devices that hold the fin on the surfboard. This makes it important to choose the system you want, as it affects all your fin choices for that surfboard in the future.

First, consider these fin characteristics:
Depth - The maximum height of a fin as measured from the bottom surface of the board. This shows how far the fin goes in the water. The hold of the surfboard increases with more depth but generally makes it harder to turn as well. 3-4 inch depth is standard on tri-fins and longboard single fins typically have a depth of nine inches.
Template - The fins outline.
Base - The length of the fin where it joins the surfboard. Increasing length adds forward drive, but makes it harder to turn. Shortboard tri-fins usually have a 3.5-4.5 inch base, longboard single fins are about 6 inches.
Foil - The horizontal curve of the fin, measured from the front edge to trailing edge.
Rake - The distance between the trailing edge of the fin base and the fin tip. This is the swept back characteristic of the fin. Increasing rake increases traction.
Tip - The top third of the fin. More tip means more hold.
Flex - Stiff fins are faster but flexible fins are easier to turn.
Second, consider the brands of surfboard fins available:

FCS - These fins are the most widely used surfboard fins in the world. The great things about FCS fins are the huge variety and the availability. You can almost always find a replacement at the nearest surf shop. Since FCS is the most common fin system, most surfboards come with that type of fin box. FCS makes a huge selection of fins. For fins with a softer edge try Pro-Tech. The are compatible with the FCS boxes. Installation is with a simple allen (hex) key.
Future - Probably the second most popular fin system in the US. They have some of the lightest fin boxes around, weighing in at about 26 grams/box. There are fins system for just about any type of surfboard out there. In particular, Future fins has an excellent selection of of Quad fins. There are also plenty of foils to choose from such as Vector, Vector 2, and the Scimitar. Future fins also install with a simple allen key.
Lokbox - These surfboard fins have one significant advantage over most other fin systems; they are adjustable. You can slide them forward and back to find the sweet spot for you. They are easily adjusted with a slotted screwdriver.
O'Fish'L - This is a snap in fin system. For those that love to experiment, this might be the fin system for you. You could even slap some fins in your boardshorts and change them in the water.
4WFS - The "Four Way Fin System". Four ways as in forward/back, cant/flair, toe-in/toe-out, or an entire fin replacement. The only problem with this system is there are so many choices you might go crazy tweaking just one set of fins.
If your having a surfboard custom shaped for you, another consideration is the type of fin system the shaper has worked with before. It might be better to go with one he or she knows well rather than risk an incorrect installation of a unfamiliar one.

With so many choices of fins/companies available, you shouldn't have a problem finding something close to what you want. Study the different brands. They should have descriptions of the type of surf particular fins work best in. They usually have charts available for recommended weights of riders as well.

Once you have a system you like, it's nice if all your surfboards use those types of fins. It makes it easier and cheaper to build a decent collection of fins that you can swap around and enjoy.