Age is one factor.
And if you have a close blood relative who has had prostate cancer, you're also at higher risk. If you often eat high-fat foods, reducing the amount of fat in your diet and losing weight, if you are overweight will decrease your risk. The American Cancer Society suggests eating foods high in fiber and low in fat. If you smoke, it's also a very good idea to stop, since some studies have found a link between smoking and prostate cancer. Your physician will know the recommendations that apply to men of your age and risk level.