If you want to reduce your cancer risk, focus on these things.

We all want to avoid cancer. But when risk seems to lurk everywhere, it’s hard to know what you really need to do to protect yourself. What steps really matter, and which don’t measure up? Here’s a look at what you should sweat over — and not — when it comes to preventing cancer.

SWEAT IT

No-smoking zone Lung cancer is the deadliest cancer in the United States by far, and smoking is the single most avoidable cause. That’s why so many people are giving up the habit, says Dr. Graham Colditz, a cancer prevention expert at Washington University School of Medicine in St. Louis. By latest count, only 15% of Americans smoke, down from a high of 42% in the 1960s.

Weight and see Extra pounds can raise the risk of at least 13 different cancers. Body fat encourages inflammation, promotes oxidation of cells and weakens the immune system — a recipe for cancer, says Cynthia Thomson, a nutritionist and cancer prevention expert at the University of Arizona in Tucson. Fat in the midsection is especially risky, she says. “Even if your weight is normal, you can be at risk for colon cancer if you have a lot of abdominal fat,” she says.

The anticancer workout A regular workout can give you a definite edge against cancer. According to the American Cancer Society, staying active can reduce the risk of more than a dozen cancers, especially breast, colon and uterine cancer.

Protect your skin Although most cancers are becoming less common, cases of skin cancer — including potentially fatal melanomas — are on the upswing, according to the Centers for Disease Control and Prevention. Colditz recommends skipping indoor tanning and using sunscreen whenever you’re spending time with the real thing.

Go easy with alcohol Alcohol can help set cancer in motion by damaging cells in the esophagus, digestive tract and liver. It also raises levels of estrogen, which can encourage breast cancer. According to the American Cancer Society, men should limit themselves to two alcoholic drinks a day and women should have no more than one.

DON’T SWEAT IT

Cellphones There’s no clear evidence that the radiation from cellphones can raise the risk of cancer even slightly, Colditz says. Just as important, nobody has been able to explain how the type of radiation that emanates from cellphones — which isn’t powerful enough to damage DNA — could set cancer in motion. “The biology doesn’t support the folklore,” he says. The National Cancer Institute notes that the incidence of brain cancer has barely budged in the last decade despite the proliferation of mobile devices.

Power lines The radiation that surrounds power lines is too weak to damage DNA. And even though lots of people live near power lines, there’s no proof that those people are at a higher risk for any type of cancer, according to the NCI.

Organics When shopping for produce, don’t get too hung up on labels, Thomson says. Food doesn’t have to be organic or pulled fresh from the ground to be healthy.

GMOs Despite all of the furor surrounding genetically modified organisms, the American Cancer Society says that these foods haven’t been shown to cause cancer or any other health problem. In the U.S., GMOs have to meet the same standards of health and safety as any other food product. A study suggesting that genetically modified corn caused tumors in rats made headlines in 2012, but it was widely debunked and eventually retracted. The World Health Organization notes that “no effects on human health have been shown as a result of consumption of such food.”