NEW YORK (AP) _ Comedy is serious business at $13.95 a copy, babe.

And so comedian Richard Belzer, sitting in the Frank Sinatra Room of the show biz haven The Friars Club, keeps a straight face while discussing his first tome, ''How To Be a Stand Up Comic.''

''Why a book? Well, no one had ever written one. And a lot of people have always asked me a lot of questions, been curious about it, and I was surprised to see that nobody had written an insider's view,'' he said.

Yeah, but is the book a joke? Or does it have some real pointers?

''There are things in there that are very useful,'' offers a still-somber Belz, whose live shows have made him the favorite comic of (among others) Robin Williams. ''Having seen hundreds of people try to be comedians over the years, I've learned some insights that I've relayed in the book.''

For example, there are tips on handling hecklers: ''What do you use for birth control - your personality?''

There are tips on jokes to avoid: ''Never, never, ever make fun of Frank Sinatra. Dead comics tell no jokes, if you get my drift.''

And there are tips on slipping funny country names into your stand-up: ''Cameroon, Lichtenstein, Canada, Lapland and, of course, Sri Lanka.''

Belzer, who declined to give his age, was born in Bridgeport, Conn. He did not complete college, and claims he was asked to leave because of his ''uncontrollable wit.''

He has never written any previous books, but has appeared in several movies, including ''Night Shift'' with Michael Keaton, and ''Scarface'' with Al Pacino. He also was co-host of a morning radio show, a cable TV show ''Hot Properties'' and appeared off-Broadway in ''The National Lampoon Show.'' He lives with his wife and two daughters in Manhattan.

Belzer started performing as a stand-up comic in 1972: ''I'd done everything else in my life. I was a teacher, I was a census taker, a jewelry salesman. I was a free-lance writer.

''And finally, I just wound up saying, 'Well, I've been funny all my life, let me try and make a living at what I should be making a living at.''

In his first two times onstage, he experienced the high and the low of the business.

''The very first time I was on stage, I was at 'The Escape Hatch' in New Jersey - that's where I killed,'' he recalled. ''First time I ever performed, for some reason, I just did great. And then I bombed at Max's Kansas City.''

Since then, it's been mostly highs for Belzer, who lists his favorite comics - Albert Brooks, Richard Lewis, Jay Leno, Gilbert Gottfried - but refuses to name those he finds unfunny.

''Can you imagine if I gave you one name?'' said Belzer, finally breaking into a smile. ''It would reverberate through the echoes of the industry.''

After loosening up a bit, the comic then provided a Belz-eye's view of several public figures.

- Preacher-patron Jimmy Swaggart: ''I think he's proved you can apologize to anything and get away with it, 'cause he apologized to his son, his wife, his car, aluminum. He sinned against everything. So he set the world record for apologies.

- President Ronald Reagan: ''Well, I'm going to miss Ronald Reagan. But he's not gone yet. We may be in Nicaragua sooner than you think.''

- Mayor Edward I. Koch: ''I think he's a self-serving, demagogic, megalomaniacal fool, with one of the most corrupt administrations in the history of the city. But aside from that, he's doing a good job.''

Finished here, a serious Belzer goes back to the serious business of promoting his book and providing advice to the aspiring laugh-getter.

''Don't give up too early, 'cause it's very hard. It's discouraging, but if you really want to do it, it's great,'' he said. ''I mean, it's great if you can make a living at being a comedian. It's a wonderful thing.''