Those of us who have lived in a city for most of our lives get to thinking that by now we're street-wise: Nobody's going to be able to pull a fast deal on us. We may not be as savvy as we think.

Peter T. Maiken, a 45-year-old Chicago editor, talked to 200 workers -- the kind you meet when you go shopping or get medical attention or want to have something repaired -- and they all claimed that in one way or another they had bilked us out of our money, or knew somebody in their workplace who did. Sometimes it wasn't intentional, but usually it was.

Maiken has compiled 100 of these interviews in a new book, "Ripoff: How to Spot It, How to Avoid It" (Andrews and McMeel, Inc., 285 pages, $5.95 paperback). Here are some samples:

A shop foreman in the carpeting business warns that if the customer leaves it up to the salesman to determine how many square feet the living room floor is, the customer may end up paying for more wall-to-wall shag than what is installed. Measure it yourself, he says.

If you don't calculate your parking cost before handing over your stub you run the risk of a hiked charge, says a parking garage attendant. "I have made $190 in one night, mostly from overcharges," he tells Maiken. "People don't pay any attention . . . "

A supermarket meat wrapper says her store advertised three different kinds of ground beef, one more expensive then the other: regular ground beef, ground chuck and ground round. "But," she says, "basically there wouldn't be any difference among them: they were all the same." This, says Maiken, is the ripoff that surprised him the most.

A life insurance salesman advises that you read the policy carefully before you sign. What's down on paper may not be as beneficial as what your hard-sell agent is telling you.

An auto transmission mechanic says his shop usually replaced only a small portion of the transmission fluid, even though "it is essential that you replace all the fluid in the trans every 25,000 miles." The customer, he says, was charged for a complete 13-quart change of fluid, and the car was on the road to a breakdown.

Maiken's book is the result of experiencing what he felt was a ripoff. He paid rent on an air-conditioned apartment, he says, but when the system broke down one hot summer the management failed, for weeks, to repair it.

"The idea (for the book) came to me like a cool breeze."

It's not a pleasant world Maiken presents, with somebody out there ready to get you at every turn. The nation has gone through 20 years of "moral unloosening," he says. "Standards of public decency and manners have perished."

In his profession -- he's senior editor of The Chicago Tribune Magazine -- Maiken concedes that he's expected to be "a bit skeptical, even cynical." But, "I'm more watchful than before. You notice it in city living; in the country, you drop your guard."

The other day, he says, he caught a big-city hotel trying to "tack a phony phone charge on my bill" for some uncompleted calls. Parking attendants have tried to overcharge him, he says, and cocktail waitresses sometimes give him somebody else's higher tab.

Most of the people Maiken interviewed are from Chicago. Those who witnessed ripoffs, he says, talked to him "out of a sense of righteousness." Those who perpetrated ripoffs had a variety of reasons for talking. "Some did it out of a sense of bragging, proud of their execution -- 'Aren't I a sharp conman?' Some probably needed a priest to confess to . . . "

And, he says, "a lot of ripoff people actually wanted to help people out."

Most, but not all, of the 200, Maiken believes, are "fundamentally honest people," who felt they were "prisoners of the system." He says he doesn't mean "to indict" others in the same occupations. "I'm not saying these people are speaking for their profession. They're just talking about their corner of the universe."

To avoid getting ripped off, Maiken advises:

Inform yourself through the media and consumer organizations about the marketplace. "It is common sense."

Comparative-shop. "We know we're supposed to do it, but we don't."

Always get something in writing. People will give someone $400 for a roofing job without a contract, he says, and that's not wise. "You've got to have the paper to prove your point" if something goes wrong.