There's no way to be sure you'll never get cancer. However, some things can lower the risk of certain cancers:
Don't smoke and avoid being around smoke: Lung, kidney, bladder, head, neck, mouth, and tongue cancer
Don't use smokeless tobacco (snuff or chew): Head, neck, mouth, and tongue cancer
Don't drink too much alcohol: Head, neck, liver, and esophageal (the tube that connects your throat to your stomach) cancer
Avoid prolonged exposure to sunlight and use sunscreen: Skin cancer
Be careful at work so you don't come in contact with chemicals that can cause cancer: Various cancers
Get vaccines that can prevent types of cancer that are caused by viruses:
Not everyone needs the vaccines, so talk to your doctor about whether you do.
Screening tests to find cancer early aren't really prevention. However, cancer treatment works best when started early. Talk to your doctor about whether you should have screening tests such as the following:
Other tests may be appropriate if you have increased risk of certain cancers (for example, a cancer that runs in your family).
Doctors don't know for sure whether diet and physical activity will keep you from getting cancer, but they may help. In any case, these things are good for you to do: