Two weeks ago, an estimated 20 million American smokers tried to kick the habit during the Great American Smokeout -- the day-long smoking cessation program sponsored by the American Cancer Society.

Figures of how many people succeeded in going smoke-free for the day are not yet available. But if last year is any indication, some 5 million people made it through the day. But 17 million -- 85 percent -- were smoking again within five days.

As for those people, experts say, keep trying. Studies show it takes the average smoker at least three tries before they succeed in quitting. Psychologist Lynn Kozlowski, who specializes in smoking research at the Addiction Research Foundation in Toronto, recommends these steps for smokers who haven't been able to quit but would like to lower the damage of cigarettes:

*Smoke as few cigarettes as possible. Studies show that even two- and three-pack-a-day smokers have been able to cut back to half a pack or less a day.

*Never smoke more than two cigarettes an hour.

*Smoke the lowest tar and nicotine cigarettes acceptable, and when you get used to that brand, switch to a lower one.

*Take fewer puffs per cigarette. Even with a low-tar cigarette, taking extra puffs can dramatically increase the amount of tar and nicotine consumed.

*Leave longer butts, since the last part of the cigarette delivers the most nicotine, carbon monoxide and tar.

*Try not to inhale, but if you must, take shallower puffs.

*Do not keep cigarettes in your mouth between puffs.

*Avoid blocking the vent holes on filters, which increases taste but also delivers a much higher dose of nicotine, tar and carbon monoxide. After smoking, look at the filter. If there is a bull's eye stain -- brown tar surrounded by white filter -- the vent holes were not blocked. If there's a uniform brown stain across the entire filter, the holes were blocked.

For those who did quit and would like help making it through the holidays smoke-free, the American Cancer Society offers "How to Stay Quit for the Holidays," a free pamphlet on maintaining smoking cessation, available by sending a stamped, self-addressed envelope to the American Cancer Society, 1825 Connecticut Ave. NW, 20009. 483-2600.