What is the best preventative measure a person can take against cancer?

Preventing cancer: Good nutrition every day is probably the most profound overall thing you can do to prevent cancer. Lean proteins, plenty of veggies and fruits (organic if possible, especially if on the "dirty dozen" list for pesticides), and lots of fiber, good water, & healthy fats. Consistent exercise and sleep also. These measures help keep your body in good tune, and manage weight. Plus, don't smoke!

Don't smoke: Tobacco is a risk factor for many cancer types.So don't smoke. Additionally, some would argue maintaining a diet rush in vegetables and low in red meat (http://en.M.Wikipedia.Org/wiki/the_china_study_(book)). Maintain suggested weight- obesity seems to increase risk. Stay as lean as possible. Exercise decreases risk. Decrease alcohol consumption. Decrease stress. Follow recommended screening tests.