Sometimes the best way to plan your future is to get an angle on the past, historians say and for kids, the past is all prehistory, since it predates their arrival on the scene. That may make it the best place to start.

The way archeologist Steve Shepard tells it, your back yard may be riddled with artifacts that, with a little digging, could teach us much about how our predecessors on the Potomac lived. "It's not even necessary to dig this stuff out," says the assistant director to Alexandria's Archeological Research Center, "since everything from erosion, roots and construction to plain old rain brings it to the surface." Some 96 different prehistoric sites have been located within the city limits of Alexandria alone, and Shepard believes that sharp-eyed searchers could turn up "chips, flakes, arrowheads or colonial trash" nearly anywhere in the area.

But don't do it, he says: "You can really mess up precious archeological messages from the material's environment."

He applies this warning with the force of a lifesaving tourniquet: "Do not disturb any site you have found. If you think you've located something historic or prehistoric, call the Alexandria Research Preservation Office if you live in this city [750-5798] or Rex Wilson, senior archeologist at the National Trust for Historic Preservation [673-4000], and we'll tell you what to do."

The Historic Preservation Office of D.C.'s Department of Housing and Community Development is particularly adept at coping with trash from the past. A new law requires that an archeological statement be filed for every federally funded construction; the office is responsible for this in the District.

Geoff Gyrisco, at that office (724-8790), can tell you what digs are on each month; just now, he's following work under the old Willard Hotel and in the Navy Yard Annex along Metro's Green Line. If you hit him on the right day, you might be able to trot your tots down to a dig and see prehistoric stone flakes, Federal-period foundations or something as exciting as a recent find in Mitchell Park -- the start of a 1790 house owned by the German Empire, and seized by our government during World War I as "alien enemy property."

Digging up arrowheads and bodies is only part of archeology, however. Most of the science relies on asking basic questions about human behavior, and using the past's scanty clues to solve mysteries that would baffle whodunit connoisseurs."Some we just never solve," admits Shephard, "like the loaded gun we found in an abandoned well. The rifle's butt was busted, but the gun was perfectly usable, and ready to shoot." Was there a fight? Or was it owned by a rich man, who didn't consider the rifle worth repairing and inadvertently left it loaded? Maybe the rifle is a missing clue to a long-forgotten murder, a weapon quickly stashed down the old well.

Less dramatic questions than these -- but more practical, as far as the archeologist and interested amateur are concerned -- revolve around the way land, food, clothing and material goods are made, used and stored Shephard advises children, and even their parents, to take a fresh look at their own homes and neighborhoods and then travel to one of Washington's plentiful "living history" experiments, applying the same questions and comparing the results:

Do you have a yard? Are there any buildings on it besides your home? What are these buildings for? Where do you keep your trash? Are there fences on your land to keep your animals in, or your neighbors out?

How large is your home, and what style is it? Why did you choose this home? How many rooms do you have, and what are they used for? What are some things you usually do inside? Outside? What does this tell you about your home?

How do you get your heat? How do you cool the rooms? Do you have windows? How are they covered? How is your home protected from burglars?

Do you have any animals? What for?

What kind of food do you usually eat? Where do you get it? What things make it hard for you to get food, and what things make it easy?

How many things -- items you would take with you on a move -- are in your house? Your room? (A recent well excavation in Alexandria turned up more than 16,000 items, so this question can take some time to answer). How many of your things are necessary, and how many for decoration?

If everyone moved away from Washington today -- perhaps due to an extreme hot-air leak -- and you were magically transformed into part of a team studying the site in the year 3000, what do you think you would find? How would you date the site? (Hint: Look under fence posts, to see what kind of things dropped into the holes.) Where do you think you would start digging first? (Hint: Think garbage.) What do you think you could tell about the people who lived here, from the questions you have answered?

A group of neighborhood children, from four to 13, set out with these questions and immediately got bogged down trying to count the family possessions. We cut back to counting those owned by the children, which still numbered in the hundreds.

When we arrived at the site of our choice -- the poor, backwater, 18th-century Turkey Run Farm in McLean, Virginia -- the four-year-olds queried an authentically grubby park attendant, and the 13-year-old tried to count children's possessions. She found three: A set of clothes, an extra shirt, and a blanket. Not a Barbie doll, a pinball machine or a laser gun in sight.

Another dramatic difference in lifestyles came with the delicate question of trash: "We don't have any," a woodchopping ranger informed us. "If it's edible, we feed it to the hogs; it it's not, we burn it; if it breaks, we fix it; if it tears, we mend it."

Gee, we're really wasteful," said ten-year-old Sherry Nyman.

What would it be like to grow up without toys or trash, we wondered. "Pretty dull." eight-year-old Wendy Luedtke retorted. Her sister, Debbie, tied this to our wastefulness.

"We've thought up all these machines that do our work for us, so we have lots of extra time to do unnecessary stuff," she said, "like play with toys, and go to school. The kids here had a lot more work to do, so they didn't have to go to school."

And when the children on Turkey Run grew up, what would they be educated to do? "Farm!" came the chorus.

And is the farm poor or rich? "Poor," they moaned.

So what would the kids be when they grew up? "Oh," came Debbie's tentative conclusion, "they would be poor."

And what would the children's children be?

"They could go to school and learn something else," insisted Sherry, our resident optimist.

Like the children in our group? "Yeah," came the uncertain replies, "like us."