My car recently broke down. Since my friendly, smiling mechanic convinced me that I had inflicted a great deal of misery upon it by driving with broken hoses and no water in the radiator, I decided to trade it in.

He referred me to a friendly, smiling car salesman.

"They're great cars, in such high demand, you get excellent mileage. We've been selling them like crazy," he said about a car I was considering.

The sales pitch sounded impressive, but after a brief test drive, I told him I had to look around.

"This is the ONLY car left. How about putting down, say, a $100 deposit so I can hold it for you. Then on Monday, if you decide you don't want it, we'll tear up the check."

That sounded innocuous enough, and it gave me time to check other dealers' prices. Most prices were similar, but one dealer offered the same car for $200 less.

"I decided not to get the car," I told the salesman over the phone.

"But you already bought it," he replied.

"No, I didn't. I only put down a deposit."

"What's he offering you?" His voice was rising. "Another dealer can't possibly offer it to you any cheaper. Besides, I'm even throwing in a fifth speed for free."

Aha, the bargaining begins. Finally.

It turned out, ultimately, that both deals were essentially the same. So I stayed with the first salesman and picked up the car the following morning.

While signing the papers, I noticed a deposit slip dated a few days ago. "You told me you would NOT deposit the check," I said with a glare. He looked embarrassed and mumbled, "We could have retrieved your money, somehow."

When I left, he said, "You're a tough customer."

Whether or not that's true, all new-car customers have to exhibit some form of toughness, not only to get the best deal, but to avoid being ripped off.

The customer should know how to connive. For example:

"Another dealer will give me $300 off since I'm paying cash. What will you give me?"

Or: "I'm getting a few free extras from another dealer. What will you offer?"

Or: "If you throw in a radio and an automatic transmission for free, I'll buy it right now."

Aside from conniving, there are specific guidelines each customer should be aware of. A spokesman for the Automotive Trade Association, a lobby group that mediates consumer-dealer problems, lists these steps:

1. Read Consumer Report, Motor Trend magazine and Road and Track magazine for information about current list prices, performance capabilities and reliability standards. Be familiar with the various list prices for each car to know what price to barter for.

2. Shop around. Go to several dealerships and try several cars, large and small, even cars you may not be interested in, to get an idea of the various packages on the market. Also avoid purchasing a car purely for emotional reasons; force yourself to look around.

3. Be sure to test-drive a car in both the city and on highways. The difference between highway and city driving, especially with smaller cars, can be noticeable.

4. At foreign dealerships, bargaining may be difficult since the demand for small imported cars is high. Prices may be close to or even higher than basic list price. But again, price-shop both large and small foreign car dealerships.

5. Read carefully all material so you know what you're buying. Check out warranties, financing, extra costs and do not agree to anything extra until you are informed of the price.Dealers have been known to make small fortunes with extras and customers can be misled by the lure of added attractions.

6. Do not make a final decision until you are certain you want the car. Most dealers will not give you an exact price until they are relatively sure you want to buy from them. Work with the price range they give you and barter. Most dealers charge the same price for preparation and handling, and for destination handling, but again, check prices at different dealerships.

7. On trade-ins, bargain as much as possible, remembering that dealers will not give you as much as your car might be worth on the open market. Refer to the blue book, the NADA Used Car Buying Guide, to get an idea of what your car is worth.

8. If and when you have problems, either with a dealer or with your new car, there is always the Better Business Bureau and AUTOCAP.

AUTOCAP is an automotive consumer action program sponsored by the Automotive Trade Association, National Capital Area. The association serves as an in-house mediation group that listens to both the dealer and the consumer.

"There is a fee for dealers to belong to the group. They are essentially paying the organization to handle customer relations," explains Patricia Vinscavich, a consumer adviser for the association. "There is no fee for the consumer. About 150 dealers in the Washington area belong to the association."

I must admit I like my new car and I hope it will last at least 10 years. For if I have to go through buying a car before that, it will be too soon. Much too soon.