IT TAKES A good case of "I'd rather do it myself" to get up at 6 in the morning, pack the car with cardboard containers and Tupperware and drive an hour to a farm in the country just to pick strawberries. It takes endurance to play unaccustomed laborer for a few hours, but it helps to think of strawberry pie or strawberry jam.

Mostly, it takes stoicism. After the field boss has assigned you your row and you have picked clean, say, 40 little plants on either side, thigh muscles start to ache and twitch and standing up brings an "unhh." You're compelled to stop squatting and sit down. You descend onto the berry bed - carefully, or so you thought - as juice from mushed berries seeps into the seat of your pants.

Rule No. 1: Never pick berries in clothes you want to wear for anything else.

Several farms in the area offer fruits and vegetables you can pick yourself. This is the farmer's way of reducing costs with cheap labor - you. From time to time, a pick-your-own farm closes for the day to allow produce to ripen, so be sure to phone ahead the day of your visit.

Late spring, cool weather and rain have combined to slow down harvest times by about two weeks, so strawberries and peas hereabouts are pickable through most of June.

Picking peas is a dryer, neater job than strawberry picking. At least that's what it's like at the Gallahan farm in Clinton of a Sunday morning. Weighing in our containers at Cherry Hill Produce stand at 8:15, we bump into a couple from the neighborhood who, in 45 minutes, have filled an enormous cooler and a bushel basket with freshly picked peas. They advise us not to jump rows and not to talk to each other. They've picked 50 pounds of strawberries this spring, so they know about efficiency. What's makes this efficiency more amazing is the fact that, from the looks of things, their family's expanding this month.

Five years ago there were raspberries in the north field. My parents and brother came down from New Jersey to pick them, and we all filled quart boxes, except for my brother, who kept to himself at one end of the field and wasn't hungry for lunch that day.

This year, there are no raspberries at Gallahan's. Installing a sewer pipeline under the field took precedence. Pat Gallahan, the farmer's wife, says the raspberries will be back next year. So will my brother.

Strawberry plants are more amiable, anyway - no scratchy places. In the strawberry patch, a young picker just starting out calls to his mother, "I've got 14!" Then, "I've got 27!"

Kids who have been there longer have invented a game with the ripest berries. A dad objects: "Hey, stop throwing those things!" "We're only throwing the rotten ones," his daughter replies. "Yeah," he says, "that's what worries me."

Later, at the pea patch with paper sack in hand, you wonder what the dozen or so pickers are doing there. You don't see any pods at all - just lowly plants in baked earth. Surely, that efficient couple has picked them bare. Or maybe you should've gotten there at 7:30 as the fields opened.

You pick one pod, another. You lift up the tender branches of a plant and find a handful. You spot two on the next row. Your eyes are beginning to expose the camouflage of the pea, and in about five minutes you're picking along with the rest of them, with a stop to swap recipes.

The cumulative wisdom of the row is this: As soon as you get home, shell the peas. Drop them into boiling water for less than a minute. Then drain them into a colander and dunk into ice water. Put the peas into freezer bags, and into your freezer.

Of course, the true pea lover won't let the peas get this far, but, knowing every hour away from the patch subtracts sweetness, will eat them in the car on the way home.

To make sure strawberries last at least that long, here's how to pick them. Use shallow containers for berries and other soft, juicy fruit: top layers can crush the ones on the bottom.You know strawberries are ready for picking when they're bright red and shiny. Some folks like them with a little green still on the bottom tip, but they're not totally rip then. To pick them right, pinch through the stem a little above the cap. Leave the cap on the strawberry. If you pull it off, you might bruise the berry, and, without a cap, the berry will dry out sooner. Store berries unwashed and uncovered in the refrigerator and use within two days.

If you want to go farther afield to pick your own in Maryland, send a self-addressed, stamped envelope to Harold Hoecker, Cooperative Extension Service, University of Maryland, College Park 20742, and he'll send you a statewide listing of farms and crops.

In Virginia, Charles Mayes, marketing specialist for the state Department of Agriculture, bemoans the fact that vegetable farmers aren't interested in his pick-your-own program. Every year he compiles pick-your-own orchard and berry farm lists, broken down by crop. Most of the farms he names are not in Northern Virginia, but near the Shenandoah, or Richmond. But if you're game, the peach orchard list should be available by the end of June, grape orchards by August and apple orchards by September. Write to Mayes at 203 N. Governor St., Richmond 23219.

Here are some approximate harvest dates from the Cooperative Extension Service at University of Maryland. In using the list as a guide, allow for changing weather's effect on plant maturity. Strawberries, for example, are two weeks behind schedule.