There are specific steps that can be taken to prevent injury that are unique to a given sport, but in general there are a few steps that apply to most people. The average person in today's world is either injured while running or while weight lifting. As a former athlete who has suffered injury I know for a fact that these two ways of getting injured are common. First always make sure that you have excellent athletic shoes. This may sound like common knowledge, but it amazes me how often people do not follow this advice. Yes, a good pair of shoes may be expensive, but so is rehab. Secondly, do not work out with too much weight or exclusively use machines. By only using machines your body's stabilizer muscles do not get the proper workout that they need. This is advice given to me by sports doctors and trainers, when I suffered a serious sports injury, but always check with your doctor to be on the safe side.