A guide to government surplus sales in the Washington area:

General Services Administration

Local auctions and spot-bid sales are held at the Surplus Sales Center at the Washington Navy Yard, 2nd and M Streets SE, Building 197. Vehicles and items may be inspected two days before a sale from 8:30 a.m. to 3:30 p.m. Items come from federal installations--except military--in the Washington area.

* Vehicle auction: Second Wednesday of every month, beginning at 11 a.m. Next sale: April 14.

* General goods: Spot-bid sale every other Thursday, beginning at 10 a.m. Next sale: this Thursday. You may place a written bid (on a note card provided) at any time before the sale. Do not need to be present when winning bid announced.

For information on merchandise, phone 472-2133 a day or so before.

* Out-of-town property: To be placed on bidder's list for regional sealed-bid auctions at a number of locations, write: GSA, Federal Property Resource Service, 7th and D Streets SW, Washington, D.C. 20407. Name specific items you are interested in. You will be sent a catalog when they're coming up for sale. Don't have to be present when the bids are open, but GSA suggests you inspect items beforehand.

Defense Department

Auctions or spot-bid sales are held locally several times a year at three locations. Vehicles, consumer items and other surplus or used goods originate at military installations in the vicinity of these Defense Property Disposal offices:

* Brandywine, Md: On Maryland Rte. 381 in Brandywine. Sales once every six weeks; the next scheduled for April 13. To be put on the mailing list for a catalog, phone 372-8844. Registration begins at 8 a.m., sales at 9 a.m. Property can be inspected five working days before sale from 8 a.m. to 3:30 p.m.

* Ft. Meade, Md: Building T6297 (directions at entrance gate). Sales once a month; the next April 28. To be put on the mailing list for a catalog, phone 301-677-6366. Registration at 8 a.m., sales at 9 a.m. Property can be inspected five working days before sale from 9 a.m. to 3 p.m.

* Ft. Belvoir, Va.: Building 2517 at North Post near golf course. Sales about once a month; the next April 21. To be put on the mailing list for a catalog, phone 664-6551. Registration at 8 a.m., sales at 9 a.m. Property can be inspected five working days before sale from 8 a.m. to 3 p.m.

* Out-of-town property: Large items (for example, a $50,000 floating pile driver) and large quantities of items (425 men's green overcoats) offered at regional sealed-bid sales at locations across the country. To register for specific items, write Defense Property Disposal Service, Bidders Control Office, P.O. Box 1370, Battle Creek, Mich. 49016.

Customs Service

Unclaimed, abandoned and seized merchandise sold at auction at district customs offices around the country. Washington is in Region III, which schedules at least one sale each year in Philadelphia, Norfolk and Baltimore. To receive more information and a catalog for sales, write:

* Philadelphia: District Director of Customs, U.S. Customhouse, 2nd and Chestnut Streets, Philadelphia, Pa. 19106. Next sale: April 22.

* Norfolk: District Director of Customs, 101 E. Main St., Norfolk, Va. 23510. Next sale: September.

* Baltimore: District Director of Customs, 103 South Gay St., Baltimore, Md. 21202. Next sale: probably mid-October.

* Other sales: For a list of addresses of all 46 district offices of the Customs Service, write: U.S. Customs Service, 1301 Constitution Ave. NW, Room 6303, Washington, D.C. 20229.