The only way to know for sure is through experience. You just have to try different shapes and lengths until you figure out what is right for you. But everyone has to start somewhere, and there are a few easy guidelines you can follow to get off on the right foot. The first depends on the type of riding you want to do. If you plan on doing mostly freestyle riding, that is, hitting booters, jibs, and pipes, you will want to ride a shorter board. For more of a freeride, that is, first tracks through twelve inches of pow, a slightly longer board is typically suitable.
The rule of thumb is that, if you hold the board on end in front of you, it should come up to somewhere between your chin and the bridge of your nose. If you can find a board about that long, you should be ok to start. More advanced riders can decide if they want to go above or below that range, but at the end of the day, it is a really just a matter of preference. Contact any of our Authorized Dealers for advice, they will help you figure out which board is right for you.