Cancer can be seen as striking haphazardly, but research over the past 40 years shows that lifestyle factors play a role in cancer incidence and mortality.

Dr. Graham Colditz, an internationally recognized disease-prevention expert at Siteman Cancer Center at Barnes-Jewish Hospital in St. Louis, has put together a list of behaviors that greatly reduce overall cancer risk. He suggests starting with one or two from the list. Once you’ve got those down, move on to the others.

1. Maintain a healthy weight.

It’s easier said than done, but a few simple tips can help. If you’re overweight, focus first on not gaining any more weight. That can give your health a boost. When you’re ready, try to take off some extra pounds by integrating physical activity and movement into your life; eating a diet rich in fruits, vegetables and whole grains, and choosing smaller portions and eating more slowly. Parents can limit children’s TV and computer time, give kids healthy snacks of fruits and vegetables and encourage their activity during free time.

2. Get screening tests.

A number of important screening tests can help protect against cancer. Some tests find cancers early when they are most treatable, while others can help keep cancer from developing in the first place. For colorectal cancer alone, regular screening could save more than 30,000 lives each year. Talk to a health care professional about which tests you should have and when. Cancers that should be tested for regularly include colon and rectal cancer, breast cancer, cervical cancer and lung cancer (in current or past heavy smokers).

3. Protect yourself from the sun.

While the summer sun feels great, too much exposure can lead to skin cancer, including serious melanoma. Skin damage starts early in childhood, so it’s especially important to protect children. The best way to protect yourself is to steer clear of direct sunlight between 10 a.m. and 4 p.m. (peak burning hours). Wear a hat, long-sleeved shirt and sunscreen with SPF15 or higher. And don’t use sun lamps or tanning booths. Try self-tanning creams instead.

4. Exercise regularly.

While it can be hard to find the time, it’s important to fit in at least 30 minutes of activity every day. More is even better, but any amount is better than none.

Choose activities you enjoy. Many things count as exercise, including walking, gardening and dancing. You can make exercise a habit by setting aside the same time for it each day. Try going to the gym at lunchtime or taking a walk after dinner. Many people stay motivated by exercising with someone.

5. Don’t smoke.

Quitting smoking is absolutely the best thing you can do for your health. Yes, it’s hard, but it’s also far from impossible. More than 1,000 Americans stop for good every day.

Some tips: Keep trying; it often takes six or seven tries before you quit for good. Talk to a health care provider for help. And join a quit-smoking program. Your workplace or health plan may offer one.

Also, keep your kids in mind. Don’t smoke in the house or car. If kids breathe in your smoke, they may have a higher risk of breathing problems and lung cancer. And remember that if you smoke, your children will be more likely to smoke, too.

6. Eat a healthful diet.

Despite mounds of information that can be confusing, the basics of healthful eating are quite straightforward. Focus on fruits, vegetables and whole grains and keep red meat to a minimum. Cut back on bad fats (saturated and trans fats) and choose healthy fats (polyunsaturated and monounsaturated fats). Taking a multivitamin with folate every day also may help.

Make fruits and vegetables a part of every meal. Put fruit on your cereal. Eat vegetables as a snack. Choose chicken, fish or beans instead of red meat. Choose whole-grain cereal, brown rice and whole-wheat bread. And cut back on fast food and packaged snacks (such as cookies), which are high in bad fats.

7. Drink alcohol only in moderation, if at all.

Moderate drinking is good for the heart, but it can also increase the risk of cancer. If you don’t drink, don’t feel the need to start. If you drink moderately (less than one drink a day for women, less than two drinks a day for men), there’s probably no reason to stop. People who drink more, though, should cut back.

8. Protect yourself from sexually transmitted infections.

Among other problems, sexually transmitted infections — such as human papillomavirus (HPV) — are linked to several cancers. Protect yourself from these infections. Besides not having sex, the best protection is to be in a monogamous relationship with someone who does not have a sexually transmitted infection. For all other situations, always use a condom and follow other safe-sex practices.