Don't smoke. Breaking the tobacco habit may be difficult, but it can be done. While preparing to quit, cut back on the number of cigarettes smoked daily. Many people report that stopping cigarette smoking "cold turkey" is more effective than gradually tapering off. Joining a support group may help you maintain the resolve to quit.
If you live or work with smokers, encourage them to quit and ask them not to smoke around you. If there is potential exposure to cancer-causing chemicals at work, take necessary safety measures to limit inhalation.