World Cancer Research Fund's Advice for Preventing Cancer

8 key steps to preventing cancer-

http://www.wcrf-uk.org/preventing_cancer/recommendations.htm

1. Be as lean as possible without becoming underweight.
   
2. Be physically active for at least 30 minutes every day.
   
3. Limit consumption of energy-dense foods (foods high in fats and/or added sugars and/or low in fibre) and avoid sugary drinks.
   
4. Eat more of a variety of vegetables, fruits, wholegrains, and pulses such as beans.
   
5. Limit consumption of red meats (such as beef, pork and lamb) and avoid processed meats.
   
6. Limit alcoholic drinks to 2 for men and 1 for women a day.
   
7. Limit consumption of salty foods and foods processed with salt (sodium).
   
8. Don’t use supplements to protect against cancer.

All of these seem pretty sensible to me, though I'm already a vegetarian who exercises almost everyday. I do have quite a sweet tooth though, so I should probably work more on step 3!