As a winter's worth of firewood approaches the cost of an extended Caribbean vacation, it's time to look for a cheaper alternatives. But that doesn't mean you have to burn such flotsam as empty Triscuit boxes and the less important paperbacks in your library.

It won't be tidy, but if you have no objection to a fire that resembles a half-built tract house that blew down in a high wind, then you needn't worry about keeping the fireplace full this winter. In any city, especially this one, where houses are gutted and renovated with the frightening efficiency of a DOT squad installing a boot, wood is everywhere. Everywhere. Open your eyes. Put on the work gloves. Shake out the duffel bag. Empty the trunk. Hit the streets. The world is your woodpile.

But if you're going to make a serious go at urban woodgathering, you're going to have to put up with a few inconveniences, like the rough corner of a two-by-four shredding the watch pocket of the vest of your three-piece pin stripe, or the occasional twisted nail menetrating the sole of your loafer and an inch and a half of your uncalloused foot, or the occasional tetanus shot.

Because you can't gather urban firewood only when you feel like it. That's like deciding to fish for trout for a half-hour after lunch and expecting them to bite. No way, Jose. You've got to go for all the wood, all the time, wherever and whenever you are, whatever you're wearing, whomever you're with.

Finding city firewood is more than a hobby, more than even a fulltime occupation. It's an attitude. It's a way of perceiving your environment. It's its own epistemology. All matter is divided into wood and nonwood. Esse est infernari.

Like the arcane vocabulary in a foreign language -- say, Portuguese -- woodgathering must be learned through a dogged practice: on the way to work, returning from the theater, standing in line at the 24-hour bank machine. Just as the errant apostrophe jumps out at the proofreader from a page that seems clean to the lay reader, so the piece of burnable scrap wood catches the eye of the black-belt urban woodgatherer. The practiced forager, possessed of what savants term "a good attitude," is the one who will stop a city bus -- and demand that the driver wait -- as he debarks to rip a couple of feet of heavily shellacked pine molding from a townhouse in the ripe stage of pre-restoration.

It's a simple fact of life, even in the polyurethane wonderland of the toxic '80s, that more things are made of wood than anything else. Trees still outnumber plastic 64-ounce 7-Up bottles. Don't they? HINTS:

Alleys are good, especially alleys behind houses that look like new, as in newly renovated, from the front. The old guts have to be piled somewhere. Watch for rats. They burn lousy.

Parks are good after high winds. Medium branches make excellent kindling. Take your dog along. He'll be glad to carry a piece home in his mouth, unaware of his role as cheap labor.The slats on park penches burn quite well, too, but they're tough to pry loose.

Shellacked, finished and painted pieces of wood ignite quickly and burn in colors that make any Safeway artificial log look like a black-and-white movie on a $79 Sears nine-inch diagonal. On the other hand, an entire rocking chair, if shellacked heavily enough, will burn to a depressing crisp in about five minutes, and it's sadly lacking in BTUs.

The most ubiquitous scrap in the wild woodpile is a section of a raw two-by-four. It burns a little too quickly, though, so keep an eye out after heavy rains. Gauge degree of soddenness by weight. And remember, no piece of wood is ever too wet to not burn. Some just burn really slowly. And then there's that annoying buildup of resins in the chimney that comes from burning soft wood. At best, it means hiring a sweep every few years; at worst a flu fire.

Knotty pine paneling is usually not wooden, and consequently, will not burn without releasing toxic fumes. Nor is the wooden siding on ranch wagon-model station wagons.

At two in the morning, when your cache is exhausted, winter is seeping in through the cracks in the dormers and a fine film like "Bug" is still only half finished, resist the temptation to burn your own furniture. You'll regret it in a half-hour or so. Especially if you haven't finished the payments.

If you live anywhere near a Little-League or high-school baseball field, autumn is the time to go back to the diamond and pull out all those broken bats that kids still pound into the ground in some strange ritual that no one ever explained. True, it'll be tough getting them out, since they're already below ground level. But have you ever seen a Hillerich Bradsby Louisville Slugger Dave Winfield model burn? Spectacular.

When dismantling a house, make sure that you're not dissecting a home that is still being built. And should you find yourself leaving some old house's driveway with a pile of rotting scraps under your arm just as some professional hauler, hired to cart all that potential warmth away, is driving in, smile knowingly, wink, and say "Heirloom. Lucky I could save it. This'll give my grandmother something to live for. God knows she needs it."