BEFORE YOU PICK your seat and place your bets, there's a few things you should know for a day (or night) at the races. KEEPING POSTED

Racetrack announcers and callers have a ritual lingo, but it's easy to pick up. The gate is not the entrance onto the track (or the proceeds) but the mechanical starting line, a truck with a double wing-span of metal stalls and electronic doors from which the horses bolt (hence "slow out of the gate"). The post position is the starting gate along the inside and the rail refers to the inside fence; if a horse is boxed in, he may have to swing wide and come up on the outside. Post time is the starting time of the first race of the day.

Horse races are run counterclockwise, with the finish line (the wire, which corresponds to the electric eye that trips the photo finish) around the middle of the near side; the far turn is the one to the left, and the backstretch is the last straightaway to the wire.

Silks are what a jockey wears; colors, which include silks, saddle blankets, etc., are like a stable's flag, going back to the times when most spectators couldn't read. Sulkies are the light two-wheel carts in which the drivers (not jockeys) of trotters and pacers ride. The handicap is the extra weight assigned to horses to help even out the entries' chances; handicappers originally referred to the track officials who decided those weights, but now it also means the racing observers who evaluate fields for newspapers or racing programs.

A first-place finish is a win, of course; but to come in second is to place and third is to show. If you bet a horse to win, it has to come in first; if you only bet it to show, you collect something if it finishes in any of the first three slots. A maiden is a horse of either sex who has yet to post a win; it could conceivably refer to a novice gambler as well. HOW TO BET ON HORSES

Everybody has a system; some are just more romantic than others. There are basically three types of bettors: dabblers, amateurs and (relative) pros. If you're going to bet for sentimental reasons -- favorite colors, names with special meaning -- you don't need to know how to read the Daily Racing Form. However, for the slightly more serious adventurer, it's worth arriving early the first time out to study the charts.

Charts typically list the horse's age, sex and color; its trainer and jockey or driver, dam, sire and stable; the handicap weight, and details on its last half-dozen races: the quality of the track, the horse's starting position, where it was in the pack at each quarter-mile and how it finished, along with a short evaluation of its performance ("tired"). The little exponents behind the quarter-mile positions are shorthand for distance: 1

means in first by two lengths.

This all takes a little deciphering, but once you get used to it, the chart can tell you whether a particular horse is a short-term sprinter (comes out fast, but tires early), has good staying power, hates a muddy track or just seems to lack the spark.

Harness racing is similar, but horses do not carry colors; silks are dispersed by post position, so if you like red, you're always betting for the first entry (the "one hole"). And because of the difficulties involved in manuevering sulkies, and because harness-race tracks are often smaller, the horses in the first three positions are virtually always favored to win. Maybe that's why the first three colors are red, white and blue.

An entry -- two horses listed a 1 and 1A -- means two horses are entered by the same stable and are bet on as a single entity. The Daily Double involves two consecutive races, in which you pick both winners. Exacta bets are for win and place in that order; a trifecta is win/place/show in order. Or you can box your bets -- bet two horses to finish first and second in either order.

One great advantage of computerized betting is that the odds are constantly being recalculated, and you can follow the changes on the big electronic board in the infield as well as on the TV screens. The other is that you don't have to figure it up yourself. Just tell the teller which horse and how much you want to bet ($2 is the minimum), and you'll get a printed receipt like a movie ticket; if you win, you can either cash it in immediately or save them up till the end. (To get an idea of how tricky it was in the old days, go to one of the traditional steeplechase meets like the Gold Cup and watch the bookmakers feverishly chalking and changing the odds on their little slates.)

Odds are listed them-you: 10-1 means if you bet $2 and win, you'll get $20. This makes longshots potentially valuable, of course, but things can change rapidly; if you spot a promising horse with long odds, chances are a lot of other people suddenly will, too, and the odds will get a lot shorter. Odds of 1-1 or worse (2-3) means a horse is so prohibitively favored (the "odd's-on" bet) that everybody's picking it (i.e., it's not much of a gamble) and you can't make any money. However, one way around that is to bet an exacta, the favorite and a longshot, and hope your dark horse sees the light.

One other tip: When reading a horse's previous times, also check the stakes in his earlier races; if a horse has come down -- that is, if he used to be entered in higher-paying races -- he must have shown stakes potential somewhere along the way.