Sometimes you need a little know- how to take full advantage of the biking opportunities around Washington. Here's a sampling of clubs, tour groups, maps and publications to give you a head start. Bike shops sell many of the items and can help you get information about others.

MAPS AND PUBLICATIONS

GREATER WASHINGTON AREA BICYCLE ATLAS -- Definitive bike book, with maps of 68 favorite rural bike rides from the Washington Area Bicyclists Association and American Youth Hostels Potomac Area Council. New enlarged edition comes out in May. About $6.

CYCLEWAYS I & II -- Map books of 94 scenic, nearby rural rides in Maryland and Virginia. Cycleways Inc., P.O. Box 5328, Takoma Park MD 20912. $5.95 for Cycleways I (Maryland) and $6.95 for Cycleways II (Virginia).

ALEXANDRIA -- Map of city bike routes, free by calling Department of Recreation, 838-4343.

ARLINGTON COUNTY -- Bike route map of county, free at libraries or by calling 558-2941.

MONTGOMERY COUNTY -- Bike map, at libraries, county liquor stores, bookstores and bike shops, $1.50.

NATIONAL PARK SERVICE -- Free brochures with maps of trails for Rock Creek Park, C&O Canal Towpath and George Washington Memorial Parkway are available free from the Park Service Information Office, 1100 Ohio Dr. SW, Washington DC 20242; call 426-6700.

PRINCE GEORGE'S COUNTY -- Bike map, $1 by mail, from the Parks and Recreation Building, 6600 Kenilworth Ave., Riverdale MD 20737-0486; call 699-2407.

WASHINGTON AREA BIKE MAP -- Giant 1983 map, provided by Metropolitan Washington Council of Governments, listing virtually all regional bike paths and streets designated as bike routes; $5 at some shops and COG headquarters weekday afternoons, or by mail, 1875 I St. NW, Washington DC 20006.

W&OD BIKE TRAIL -- Map gives details of 45-mile route from Shirlington to Purcellville. New edition available end of April, about $3 at parks and by mail from Northern Virginia Regional Park Authority, 5400 Ox Road, Fairfax VA 22030; call 352-5900.

BICYCLE CLUBS AND GROUPS

AMERICAN YOUTH HOSTELS -- Potomac Area Council, 1331 I St. NW, Washington DC 20005; call 783-4943.

LEAGUE OF AMERICAN WHEELMEN -- National bike club, dating from 19th century, publishes informative magazine and almanac of nation's bike clubs and maps; sanctions many national 100-mile rides. Has a hospitality list of thousands of members who put up touring cyclists at their homes free. For information, write the league at 6707 Whitestone Road, Baltimore MD 21207, or call 301/944-3399.

OPEN ROAD BICYCLE TOURS -- Weekend and longer tours of mid-Atlantic states, staying at inns; plus foreign tours in China, Egypt, Israel and Nova Scotia. 1506-C Belle View Blvd, Alexandria VA 22307; call 768-8687.

OXON HILL BICYCLE CLUB -- Sponsors country-road rides in southern Maryland, P.O. Box 81, Oxon Hill MD 20745.

POTOMAC PEDALERS TOURING CLUB -- P.O. Box 23601, L'Enfant Plaza Station, Washington DC 20026; call 363-TOUR.

RESTON BICYCLE CLUB -- Sponsors rides near Reston, P.O. Box 3389, Reston, VA 22090; call 860-0112.

WASHINGTON AREA BICYCLIST ASSOCIATION -- One of nation's largest urban bike activist groups, it keeps up to date on laws, accidents and everything affecting local commuting and recreational cycling, 1332 I St. NW, Washington DC 20005; call 393-2555).

ADVENTUROUSLY YOURS -- Day and weekend bike and outdoor trips, P.O. Box 894, Rockville MD 20851; call 949-1766.

BIKECENTENNIAL -- Creator of the 4,280-mile TransAmerica bike route and interstate bike routes across the nation, including a Virginia Loop Trail. Sponsors group rides on its routes. P.O. Box 8308 Missoula, MT 59807; call 406/721-1776.

CHESAPEAKE AND SHENANDOAH BICYCLE TOURS -- Weekend and longer tours of mid-Atlantic states with overnights at inns; plus trips to Italy and Barbados. P.O. Box 21001 Washington DC 20009; call 332-7166.

WASHINGTON WOMEN OUTDOORS -- Offers day and weekend bike and outdoor trips for women, and even bike repair classes, P.O. Box 301, Garrett Park MD 20896; call 797-8222. BIKING AND METRO

Bike-on-rail passes, $15 for five years, let you take bikes to be carried on subways weekends, holidays and nights after 7 p.m. -- if you attend a brief training session at Metro headquarters, 600 Fifth St. NW; call 637-1327.