There are many useful Web sites dedicated to the sport of geocaching

Go to www.geocaching.com. Plug your zip code into the box in the upper right hand corner (or postal code if you're Anglospherical, other). A page of cache listings tumbles out. Click the link to the first one. Read the description. Input the coordinates into your GPS dingus. Hit the Go To button. Follow the arrow until you find yourself standing next to a Rubbermaid Serving Saver.

That's what I did, anyhow. Didn't even look at a map. I hopped in the car and lit out after that arrow like there was a string tied to the cache, and it's a little miracle I didn't find myself stuck up a dead end (or a tree), or drive across someone's lawn (or granny).

I followed the arrow to an unfamiliar neighborhood and a small suburban park with one sad, lonely clump of trees. I slashed my way through the middle of it like Weasel of the Amazon, emerging near the swing sets, bruised and scratched but triumphant. (Well, sort of. The cache was frozen in place and I couldn't sign the log book, so some would say my first cache got off on a technicality).

The traditional

At its most basic, a cache is a waterproof container with a logbook in it. The log book is the star of the show. This is where everyone makes his mark. Hooty hoo! I conquered the Tupperware! (You actually have to say that out loud. It's a rule).

I draw little weasels. If it's raining or I'm waving away mosquitoes the size of pigeons, they are very bad little weasels. But I reckon nothing says "my god, a weasel's been at this cache!" like a cartoon stoat.

A traditional cache also has a small amount of space for "trade items" — toys and tchotchkes and bits of junk. The rule goes, if you take something, leave something as good or better. In practice, the contents of a cache are seldom very exciting and tend to get weirder and crappier with time.

I don't think this is (just) about people being a little selfish when nobody's looking. There's something pagan and atavistic in the way people approach these boxes in the woods. Many cachers have a "signature item" (some of which are way cool and some...not) that they leave in every cache. Some move items around from one cache to another. Some will grab an acorn or a stick from the ground near the cache itself and put it in the box. Some leave money. My favorite was a soggy and disgraceful old cigarette with the note "we didn't have anything else to leave." Like the genius loci would be cross if they didn't leave something.

The micro-cache

A micro-cache is just like a real cache, only smaller. Sometimes so small it will only hold a strip of paper for the log; sometimes large enough for a few tiny trade items. Microcaches are often hidden in urban parks and busy public places where a larger cache would attract unwelcome attention, but a grown woman walking in circles muttering to herself and staring at her palm is smooooth.

Hiders sometimes exercise extreme creativity with micros, hand-crafting containers that look convincingly like dog poo or a bolt on a guardrail. Others find a ready-made film canister or Altoids tin. As it turns out, there are apparently people who enjoy standing in a field of a thousand small rocks looking for a fake small rock. It's important that we don't let our contempt for these people swell into hatred, though it's probably better if we don't let them breed.

The puzzle cache

Ach! YARRRRGH! Ptoo! Ptoo! It's a geocache with math.

Say, the first set of coordinates takes you to a memorial plaque. You read it and take the last two digits of the year the little dog died and multiply it by the average temperature on the surface of Venus (dayside or nightside? It doesn't say). Then look down at your feet and count the number of bricks on the sidewalk between where you're standing and Schenectady, New York (dayside). Now, think of a number between one and seven, dress up like your favorite Renaissance painter and divide by zero. The resulting string of numbers is the coordinates to the cache, which you must punch into your GPS receiver strictly with your elbows.

Feel free to hate puzzle cachers. They've earned it.

The multi-cache

A multi-cache is a series of waypoints, each of which has a set of coordinates or a clue that leads you to the next waypoint, with the actual log book and trade cache at the final stage. I put off my first multi until I'd done over a hundred caches. I mean, five micro-caches in the woods for one lousy find? Even I can do that math.

But now — whaddya know? — they're my favorite kind, despite all the ugly things I said about micros and puzzles above. Oh, sure...sometimes I've got two arms up a thornbush pulling myself out of a sucking pool of rancid ooze and I think, "I'm all by myself half a mile into impenetrable swamp looking for a babyfood jar that may not be there any more and I just lost GPS signal! I'm a genius!" But, after all, I only had to find the one parking spot.

The usual multi hereabouts is a series of little containers with coordinates written in or on them scattered over a big patch of woods. Another variation, common in Britain, uses puzzles caches as stages. Like, you find informational signs and work out the next coordinates based on what they say. It's a good way to lead someone around urban or historical places. There's one in Canterbury (which is both urban and historical), which looks especially cool. Only, I've never successfully completed a puzzle cache all by myself. Ever.

Virtual and locationless (reverse) caches

I get these two confused. Neither one has a logbook for me to draw little weasels in, so what's the point?

A virtual cache sends you to the coordinates of a place of interest. To prove you actually went there, you take a picture of yourself or answer a question about the place in an email to the owner. This is appropriate where a physical cache isn't, like somebody's grave. For the record, I wouldn't mind having a physical cache at my grave. Especially if it were full of chicken bones and caramel and made a loud bang when you opened it.

A reverse or locationless cache describes a sort of thing you have to find, and then you go find it. To claim the find, you post a photograph of your GPSr next to your local football stadium or nunnery or giant creepy fiberglas icecream cone top-hat lady.

So what's the point, Auntie?

It's surprising how swiftly and thoroughly addictive geocaching is. Most caches combine a nice drive in the country with a nice walk in the park with a bit of a treasure hunt, plus a toy prize, a cartoon weasel, a short essay and one up on your "found" column. What's not to love?

In the beginning, they're all fascinating. You wouldn't believe how many funny little semi-forgotten bits of land belong to Us the People until somebody sends you to a park bench and a memorial plaque smack in the middle of sweet nowhere-at-all. There are battle scenes and three hundred year old oak trees and old mills and ruined farmhouses and haunted mansions and ancient cemetaries and abandoned asylums. There are pristine animal sanctuaries and quirky urban memorial parks. There are working farms that allow public access and hundreds of acres of public land so surrounded by development that you'd never know they're there if someone didn't lead you to the trailhead.

That's the best part: finding fantastic places to hike that I would never find on my own. Not just someone's favorite park, but his favorite spot in his favorite park; that cool rock formation I wouldn't find on my own in a month of Sunday hiking trips. And somehow knowing there's a Rubbermaid sandwich keeper just one thousand feet up the trail — totally lacking a cartoon weasel! — makes me push myself farther than I knew I could go. I've pushed me so hard I scared myself a couple of times.

And, let's face it, if your hobby doesn't scare you once in a while, you need a new one.