I have been told that keeping your weight down, minimising alcohol intake (1 glass!) and exercising (minimum half an hour a day) are all very important. Green tea, lots of leafy greens for antioxidents ... a good healthy, low fat diet! There's lots of vitamins that different people sugggest too, but hey the list gets long! Fish oil, flaxseed, tumeric all get a mention. I went to some talks at a local Cancer support centre (Bloomhill) that outlined diet, exercise and positive thinking tips that helped to give me a focus.
Good luck!
Ann J