Where should you go to buy a bicycle and how much should it cost?

Ask a good salesman and he'll answer with another question: "What's the bike going to be used for?"

A wobbly beginner or semi-active adult should be able to find an adequate bike at an auto-supply, discount or department store for $75 to $85. Discounters may offer the same bicycles as department stores, identical but for brand, for considerable less.

Most bikes in this price range come unassembled, full assembly costing from $5 to $10 more. Unless you can tackle the intricacies of brake, wheel and chain adjustments with confidence, you may end up full of grease, with busted knuckles, and then have to pay someone to straighten things out. The cheaper the bike, the harder it is to fit and align the parts properly.

Avoid the tendency toward the trendy "10-speed," which in this price bracket isn't very good and isn't needed anyway by a casual rider. The fewer levers and gadgets the better. And don't go for the turned-under "racing style" handlebars, which are harder for a beginner to control. Choose the style permitting you to sit up straight and look around.

In considering a bike for an active youngster, the emphasis should shift from price to safety. To outfit your tiger, go to a bike shop, where the better-made models with reliable brakes and strong frames may go for $25 to $75 more but last a lot longer.

The coaster brake is nearly trouble-free and easier for an inexperienced rider to use than the caliper style with handlebar-mounted levers. Cheap caliper brakes are very difficult to keep in adjustment, so a lot of kids are riding around without any effective means of stopping.

If the frame looks cheap, it problble is. The standard boy's or girl's bicycle has a dozen or more connecting joints in its frame, any one of which can cause a disaster if it should break or separate. Examine each; if the workmanship is shabby, beware. If a frame is well-constructed, the manufacturer will back it with a warranty. If the salesman can't offer any assurance beyond, "Oh yeah, it's a strong sucker," look elsewhere.

Not the least of the considerations affecting the rider's safety is the fit.

Buying a too-big bicycle a kid can "grow into" can be a tragic mistake. A child cannot safely control a bike that's too large.

Ten-speeds are too fragile for subteens. The popular, low-slung, high-rise-handlebar models go for around $110 in a bike shop, with the good, really tough "motocross" styles starting at about $125. You can climb onto a conventional balloon-tire bike for about $135.

"Commuter bikes," used for lengthy rides to work or school, and more sophisticated long-distance machines, usually fall into the middle ground between so-so and pretty good.

If your sole concern is cheap transportation and your daily ride is no more than five or six miles one way, I suggest you go to a bike shop and invest $150 or so in a three-speed machine with sit-up "touring style" handlebars (as opposed to "racing style"), with one coaster and one caliper brake.

You can beat that price by 50 percent at a discount or department store, but in considering a less expensive, perhaps lower-quality bike, you should also consider your interest (and capability) in keeping its components adjusted and aligned during everyday use over an extended period when you "have to be there" at a specific hour. The expression "you get what you pay for " may very well have been coined by a skinned-up commuter hitchhiking with a busted bike over his shoulder.

If the cost of a good, new bike exceeds your budget, check the want-ads in the newspaper and the bulletin boards at the local supermarket or college campus. Students departing school often advertise their bikes for sale during the final weeks of classes.

Nearly all bulletin-board bikes will be ten-speeds, that being the fad. The used-bike market is not lucrative -- a machine in excellent condition seldom commands 60 percent of its original cost. You should be able to find a good used commuter bike for $100 or less and a clunker for perhaps $35. Before you invest in the latter, however, trundle it into a bike shop and ask if the cost of making it reasonably safe and servicable again is worth the asking price. Most bike shops also have good, reconditioned bikes for sale.

And then there are bikes for riding up over the hills and across the horizon beyond with that good, fresh breeze in your face.

With sturdy legs, and a strong heart, you can do that, of course, on a clunker. With patience and a set of tools, you can do it on a department-store bike. But just for a moment, let's indulge ourselves in semi-finer things, at least.

Semi-fine starts at about $175 and extends to around $325, any bike costing more than that beging as good as you will ever need, as long as it's just for fun. So what do you get for the extra money?

Cast your mind back to what we said earlier about the joints of the frame, and how critical these are to the frame's strength. On most inexpensive bikes, the tubes of the frame are joined with high-temperature welds, because this method is fast and therefore cheap. "Better" frames are fitted together at the joints with carefully brazed-on sockets called "lugs." With exceptions to be noted most lugged joints will be stronger than welded, unlugged joints.

The notched components that fit over the front and rear wheel axles are called "drop-outs." The dropouts on better bicycles are joined to the front "forks" -- and rear "stays" -- with virtually invisible, low-temperature brazing, and the area is often is often then chromed to avoid scratched paint and the rust resulting.

I said there are exceptions: The joint does not have to be lugged to be strong and safe. Some super-expensive, custom-fitted frames -- $1,000 and up for just the frame -- have unlugged, very carefully brazed joints. At the other end of the line, the "electro-forged" joints on the lower-priced Schwinns have a good safety record, though the company's better models have lugged frames. I am advised, incidentally, that their new Paramount (lugged) will go for $1,895.

Heavy, "dead" frames are made from straight-gauge, thick-walled tubing. Livelier frames are fashioned from "chrome-moly," Reynolds and Columbus "double-butted tubing, meaning the tube's walls are thicker at the joints, where the strength is needed. To get onto a chrome-moly. Reynolds or Columbus alloy frame, you will have to nudge the $300 mark -- but, if you're dreaming of long rides through the countryside, that's the only way to go.

A not-to-be-scoffed-at consideration in selecting that first "good" bike is how it looks to you. A fine bicycle is a thing of beauty and grace, and just knowing how you will look sitting on it extends your range by ten or 15 miles. Examine the paint and the brightwork carefully, the finish of the brazing around the lugs. If you can see something sloppy, there could be something sloppy womewhere else that you can't see.

Another factor is the feel of it, "the fit" as you settle onto the saddle and reach for the handlebars for the first time, the bike's lively response as you push the pedal downward, propelling yourself forward.

There are other yardsticks for "fit," of course, frame size being one of the most important. Straddle the top tube, wearing the shoes you'll wear while riding. There should be no less than half an inch, no more than an inch and a half, between you and the top tube. Depending on the angles of the frame, the top tube will vary in length. Put the point of your elbow at the nose of the saddle and extend your lower arm, fingers extended, toward the handlebars. Properly fitted, the tips of your fingers should just reach the handlebar.

Ladies'-style frames? Not if you're going to ride any real distances. The conventional ladies'-style frame flexes left and right with every push on the pedals, absorbing energy that would otherwise be working for your. The compromise "mixte style," with its down-slanted top tube, may be somewhat more efficient, but it's not as efficient as the men's-style frame.

Brakes: center-pulls or side-pulls? Listen to the salesman's opinion, understanding that this is a never-ending argument, reversing itself with periodic technological developments, the current fad favoring side-pulls.

I photographed the Tour de France and later, examining a shot of the final day's sprint through Paris, I noted that every brake unit visible in the pack was a side-pull.

As far as I know, the only rider using center-pulls was the guy who won.

Beyond that, one of the most important considerations in choosing your bike is how you react to the bike shop itself and the salesperson helping you. You're looking for a good, confidence-building, not-east-to-define feeling.