The "great boyfriend crunch" or the "great American man shortage," as it is variously labeled in articles and books, is endemic in large cities, claims Cynthia Heimel, who writes for the Village Voice and whose "Women" column premieres in the August Playboy.

"In Washington, New York and L.A., we're so top-heavy career-wise that relationships usually take a back seat to getting ahead, clawing our way to the top.

"I think people are in a lot of pain. Women are really angry because there don't seem to be enough men around. Men--and I've talked to a lot of men--are really scared.

"They don't know what they're supposed to be doing. They're scared to death of getting hurt. They're scared of being wimps. They're scared of being chauvinist pigs. They're scared of their shadows."

What she calls the "walking wounded"--a lot of available men "over, say, 23"--have been hurt too much or calloused too much. "You know, you're the tenth woman in his life and because he hasn't changed or grown or evolved, it's just going to be a sort of self-defeating situation.

"I think it's very grim out there right now, and I don't think it's very easy to have a good time."

As an antidote to all the angst--"a vicious chain of mistreatment"--Heimel has written Sex Tips for Girls (Simon & Schuster; $7.95, 205 pp.), a trenchant, racy, humorous look at the "sitcom" that's emerged in the wake of the sexual revolution.

"Nobody knows what they're doing," says Heimel, a self-described "hippie" in her thirties, who lives in New York and has a boyfriend who is "younger than I am."

"I think we can get in on the ground floor these days, sexual etiquette-wise. We can just make the rules because there aren't any."

In a chatty prose not unlike that of a slumber party for 30-year-old women, she eschews both the licentious, sleazy tone of porn and the scientific, analytical approach of the "how-to" sex manuals. "I just thought of P.G. Wodehouse when he was writing about Bertie," she giggles, "even though I was writing about sex."

When she gave her mother a copy of her book, "I wrote 'To mom, with all my love.' And then in parentheses: 'Please do not read Chapters 4, 7, 11 and 17.' But she did."

Among advice that even mothers can read, and in keeping with Heimel's philosophy that what singles need now is to rediscover humor:

Go for adventure. Cultivate a deviant attitude. Always be ready to go skinny-dipping at 2 a.m. Embrace the frivolous--dance, eat raspberries, drive convertibles, drink champagne, sing.

Tell the truth. Even though it's hard to say things like, "I'm scared that you're going to leave me."

Get on with your life. Boyfriends don't fall from trees. You're more likely to meet one if you're involved in your own life.

Embrace optimism. You can indulge in so many paranoid fantasies and try and force things into a crisis. "Do you love me, do you love me?" And pretty soon the other person is sick to death of you.

Use the phone. A woman should call a man whenever she wants to and she should have a certain friendly attitude. And don't make such a big effort, so that by the time you get him on the phone, you're so ready to be rejected you say, "So what if I'm a moron, will you still go out with me?"

Maintain manners. Give the person the benefit of the doubt and use tact, especially in bed.

Avoid ostentatious gift-giving. Never buy a man a Lear jet. Too intimidating. Never accept emerald brooches from a man you're not prepared to sleep with.

Forget over-zealous cleaning or cooking. Never spend more than an hour cleaning or you'll end up hating the guy. Never cook anything more complicated than broiled grapefruit. Beef Wellington and you'll hate him. " 'Who does he think he is making me cook this Beef Wellington?' "

Be yourself. The how-to articles are going in exactly the wrong direction. You keep going further and further away from yourself the more you listen to them. " 'How to make him like your breasts.' " " 'How to cook a midnight snack.' "

"Before you can actually ever connect with another human being," proclaims Heimel, "you have to know who you are, basically have a good feeling about who you are.

"We had many years of upbringing where we're taught not to be ourselves. Not to ask for what we want and get it. We forgot who we were really.

"We forgot that we were the ones who liked purple, that we were the ones who didn't want to go to the beach, and finally, when you're dating, your mother comes across with the goods, and says 'Well, just be yourself,' but you think yeah, but who am I?"