SELF-GUIDED TOURS: The simplest, cheapest tours are those you plan yourself. Prime sources for good nearby bicycle routes (usually secondary and tertiary roads with light motor traffic) include:

Greater Washington Area Bicycle Atlas, $10, available from the Washington Area Bicyclist Association, 544-5349. The atlas covers Maryland, Virginia, Delaware, West Virginia and Washington.

Bikecentennial maps, including the Virginia Loop Trail ($8.95 for nonmembers) and the Maine to Virginia route (the Philadelphia to Richmond segment will be available in September). Both are available from Bikecentennial, P.O. Box 8308, Missoula, Mont. 59807, (406) 721-1776. NONPROFIT CYCLING CLUBS: The following are among the most active groups that run inexpensive trips from one to many days, staying at campgrounds, hostels, bed-and-breakfasts or inns:

American Youth Hostels, Potomac Area Council, 783-4943. Request the current newsletter for information on upcoming Eastern Shore, Potomac River Valley and other trips.

Appalachian Mountain Club, national office, 5 Joy St., Boston, Mass. 02108, (617) 523-0636. Local chapter membership brings you information on trips from Maine to Virginia.

Bikecentennial, Trips Department, P.O. Box 8308, Missoula, Mont. 59807, (406) 721-1776. This service organization's most famous guided tour is the 4,450-mile Trans-America from Williamsburg, Va., to Portland, Ore.

American Lung Association, 1740 Broadway, New York, N.Y. 10019, (212) 315-8739. The association sponsors tours from three days to six weeks. COMMERCIAL TOURS: We chose Vermont Bicycle Touring for our Adirondacks and Vermont/New Hampshire trips. This is a first-class outfit featuring multiday trips in New England, plus Cruise & Cycle, Pedal & Paddle and other specialty tours. Weekend trips cost from $169 to $399 per person, inn-to-inn trips from $365 to $645. For more information: Vermont Bicycle Touring, Box 711, Bristol, Vt. 05443, (802) 453-4811.

For one-day to multiday trips anywhere from New Jersey to New Zealand, from Bermuda to Bali, there are scores of other companies offering a variety of guided tours, among them:

Cycle Tours, 2007 39th St., Des Moines, Iowa 50310, (515) 255-5352. This is a one-stop agency that books tours for many companies worldwide, based on your ability and pocketbook.

Chesapeake & Shenandoah Bicycle Touring, P.O. Box 65292, Washington, D.C. 20035, (301) 987-BIKE. This company features day, weekend and longer tours in the mid-Atlantic region, including of Civil War battlefields, the Eastern Shore, the Tidewater region. Day tours begin at $24 per person, weekends run upwards from $169.

Butterfield & Robinson in Toronto, (416) 864-1354.

Country Cycling Tours in New York City, (212) 874-5151.

Backroads Bicycle Touring in California, (415) 895-1783.

True Wheel Tours in Delhi, N.Y., (607) 746-2737.

Rim Tours in Utah, (801) 259-5223. Lists of tour operators are found in:

The March/April Tourfinder issue of the Bicycle USA magazine, which is free to members of the League of American Wheelmen Inc., 6707 Whitestone Rd., Balto., Md. 21207, (301) 944-3399.

Cyclists' Yellow Pages, which is free to members of Bikecentennial (address and phone above).