Snowboard length is usually directly related to how tall you are. One way to pick a board size is to convert your height from inches to centimeters (one inch equals 2.54 cm) and then subtract about 14 cm. For example, a woman who is 5'4" (163 cm) will usually pick a board length of around 149 cm (163 cm minus 14 cm). For those of us who could care less about figuring math equations when we are out shopping for some gear, the easiest (and a pretty accurate) way of matching the board length to your height is to pick a board that, when stood on end, will reach between your nose and chin. A shorter board is easier to control and is usually lighter in weight. A longer board carves more easily and goes faster (assuming you've got a good wax job on the base). I've seen short women with longer boards because they love speed, and it is pretty common to see tall guys with tiny little boards (around 145 cm or smaller) for exact control in the halfpipe and while performing rotational-type tricks, like 360s or 720s.
The width of the snowboard isn't as important as the length. Usually a standard width (at the most narrow part) for most boards is about 25.5 cm. However, if you happen to have big feet, and you notice that on a conventionally-sized board your toes and heels tend to hang way over the edges, width becomes a real issue. Toe and heel drag reduces your ability to make tight turns and carve. K2 makes the Fatbob snowboard, with widths ranging from 26 cm to almost 29 cm, depending on the model.
There are many types of materials that go into making snowboards. Each manufacturer likes to be different and offer a signature composite. Common materials are wood, plastic, carbon, steel, and sandwich-type composites that use several materials together. Each type has a distinct advantage. Make sure you read the manufacturers information to find out the details of your board's materials and how they translate to a better ride.
One of the last things that you want to consider when looking at snowboard form is how much flex the board has. Every board has varying degrees of flex along the length (longitudinal) or sideways plane (torsional). Some boards, by virtue of their material composition, are stiff and unyielding. This is great for stability at higher speeds but not so good for the rider who doesn't weigh much and cannot get the board to flex with bodyweight alone. The rule of thumb here is stand a board upright on its tip or tail, hold the upper end tightly with your hand, and press your foot into the middle of the board. Observe how much flex there is. You want a fair amount, but not too much, which can cause a sloppy ride.
