Before you start snowboarding
Snowboarding is a physically demanding sport, and hence you need to train before you can hit the slopes. Cardiovascular activity should be undertaken 3 to 4 times a week for a couple of weeks before you set off on your snowboarding trip, especially is you have never boarded before. This should not just be a crash course, but should greatly improve your physical shape. Make sure you choose exercise which will also increase your core muscle strength in the areas in which you will need it, i.e. your legs. Activities such a cross-training and running are ideal for this.
Snowboarders also need to be flexible so make sure that you engage in a series of stretching exercises in the weeks before you go boarding, so that you are more supple. When you are on your trip or holiday, also make sure that you stretch out at the end of everyday of boarding, so that you do not become stiff, which would greatly effect your performance.
Balance is essential for snowboarding, and can often be the area in which most beginners fall down. Doing activities such a yoga and pilates which increase your inner stability will greatly pay off in your performance on the slopes.
Snowboarding can produce some catastrophic injuries as well as some more minor ones. Improving your physical condition in the ways suggested above will dramatically reduce your chances of getting an injury on the piste. If you are fortunate enough to only incur a slight strain etc, do not continue to snowboard. This will only make the injury worse and could lead to further problems, which could greatly effect your day to day life.