With tomorrow's official kickoff of the holiday season, "now's the time," says author Richard Basini, "that provides the real test of your ability not to have that drink that's being thrust on you."

It's also the occasion, according to the American Automobile Association, when record numbers of Americans -- 29 million nationwide -- will take to the highways this weekend (6 p.m. Wednesday through midnight Sunday).

The odds are that several of them will become part of the statistics projected by the National Safety Council, that between 380 and 480 persons will die and 17,000 to 21,000 more will suffer disabling injuries in vehicle-related accidents this weekend.

Alcohol is likely to play a significant part in those sobering numbers. It needn't be that way: The ability to say no to a drink, says Basini, the author of How to Cut Down Your Social Drinking (Putnam, $13.95), is a matter of discipline.

"The allure of an extra drink," says Basini, "often cleverly obscures the benefits you stand to gain by saying no." Among the benefits he cites for cutting alcohol consumption:

*Losing weight. Drinking often can act as an appetite stimulant, adding unwanted calories to the useless calories drinking itself involves.

*Having more fun at parties. "After the first drink or two the socializing benefits of drinking drop off rapidly."

*Feeling healthier.

*Being more productive at work.

*Having money.

*Having a better sex life.

Basini's bottom line: "Successful people don't drink much. Period." He offers a three-point drink-reduction program for social drinkers who want to cut down on their alcohol consumption:

*Set a specific number of drinks you intend to limit yourself to;

*Set a time limit on how long you intend to stay at the social function;

*Know in advance why you're attending the function (if you can't come up with a good reason, don't go).

Among the tips Basini picked up:

*"I never drink standing up. I wait for dinner and then enjoy the wine." -- Critic Gael Greene.

*"Be the first to order. If you order a Perrier or a wine spritzer, nobody's going to order a martini." -- Broadway actor Jerry Ohrbach.

*"I drink an 8-ounce glass of water before each drink at a party." -- Architect Don Miles.