The Consumer Information Institute will hold a seminar on "How to Sell Your House - With or Without a Broker," March 21 at the Key Bridge Marriott. The session costs $35 for individuals or $50 for couples. For information, call 649-6666.

The apartment building called 3701 Connecticut is being converted to condominium ownership by Wlltshire Associates of New York City. Shannon & Luichs is handling sales of the apartments in the 10-story building, which overlooks Rock Creek Park. The units will be ready in late spring.

The Fairfax County Economic Development Authority has approved a $300,000 industrial revenue bond for a new warehouse-office building of 30,000 square feet in the Shirley Industrial Park near I-385 and Edaall Road. Rudalph & West Co., wholesalers of industrial hardware supplies, will use half the building and the remainder will will be leased.

The written examination for real estate brokers and agents in the District will be held starting 8:30 a.m. March 21 at Harambee House, 2225 Georgia Ave. NW.

Hallmark Development Co., Inc., of Annapolis, reported the sale of 100 lots in the Davidsonville, Lothian and Deale areas of Anne Arundel County to Jack Construction and Development, which plans to build single-family houses priced from $55,500 to $98,500.

A 20-acre tract near Pohick Church in the Loston area of Northern Virginia has been sold for more than $300,000, realtor Frank T. Skalaki, of Blue Ridge Realty, reported. The Gunston Hall syndicate sold the property to Engleside Christian School and Church, which plans a new building on the site.

Arlington Realty Corp. announced the sale of a 25,000-square-foot building at 2701 Wilson Blvd., Arlington to B & C Associates. K and E Associates was the seller. Brokers William Buck and William Coleman of Arlington Realty said that Arlington Telecommunications Corp., which has a cable TV franchise for Arlington, will be a tenant in the two-story, 50-year-old building along with Keuffel and Esser Co., a graphics firm.

KLW Design Inc., headed by Terry Korth and Charles Lemke, is working with Anton Berk in the development of nine town houses at 16th Street and Arkansas Avenue NW. They are also handling the conversion of the 183-unit 4200 Cathedral Park apartments to condonominium ownership. Korth and Lemke formerly were with Berger-Berman Builders. Berk is the son of developer Maurice Berk.

DRG Financial Corp. recently arranged the $5.4 million refinancing on the Oxford Knolls and $4.1 million on the Stratford Woods apartment in Prince George's County. The FHA Section 2230 financing was placed at 8 1/2 percent mortgage for 35 years. Both garden apartment developments are owned by groups of which Allan Stillman of New York City is a general partner.

Summa Corp., which is building traditionally styled town houses on a 15-acre tract in Burke Centre, plans to keep 11 of the acres as wooded parkland deeded to the homeowners association. Electric golf carts are being used to escort prospective buyers through the Heritage Square North development there.

Construction is under way in Isaac Newton Square in Reston on a 64,000-square-foot, two-story office building scheduled to be ready for occupancy early in 1979. Jansons Associates designed it and Gulf-Reston, Inc., is the developer.

The American Institute of Architects Foundation is sponsoring a sale of [WORD ILLEGIBLE] tints, water-colors, etchings, engravings, photographs and lithegraphs depicting architectural designs and related subjects to benefit AIA's Octagen House and architectural archives. The benefit sale will be held from 1 to 6 p.m. tomorrow and from 10 a.m. to 4 p.m. Monday and Tuesday in the galleries at Octagen House, 1780 New York Ave. NW.