Four cancer-causing behaviors to avoid are smoking/secondhand smoke, alcohol consumption, a sedentary lifestyle/lack of exercise, and an unhealthy diet. 

Smoking increases the risk of lung, esophageal, stomach, and cervical cancer. Alcohol is linked to colorectal, liver, breast, and esophageal cancer.

A sedentary lifestyle increases the chances of cancer cell invasion. An unhealthy diet, including excessive red meat and pickled foods, and insufficient intake of fruits, vegetables, dietary fiber, and calcium, also increases the risk of cancer.