Q: We are interested in selling our house. Should we sell it by ourselves or with a real estate agent?

A: A few years ago, any suggestion that homeowners could sell their own house without the services of a real estate agent or broker was considered heresy within the real estate trade.

In recent years, however, more and more sellers are finding that it is possible to sell houses without using real estate professionals. Two underlying assumptions are basic to any discussion of selling your own house:

1. Do you have time?If you are busy in your job, and will not have time to attend to the many details required in selling a house, you amy want to consider using the services of a real estate agent.

2. Are you up to doing the selling? You will have to sit in your house for several weekends, be bothered day and night by inquiries, and will have to learn some basic real estate information.

If you think you'd like to try it, here is a brief checklist:

Determine the house's market value.Go over the classified ads for several past months to determine the selling price of other houses in your area. Look in the Lusk Directory in your local library for sales prices of comparable houses. Ask local real estate brokers for their opinion; most real estate people will be more than cooperative on the expectation that they may get a listing from you after all.

Develop a fact sheet. Often, when people visit many houses on Sunday, they tend to forget the details of each and every house. It is strongly recommended that you develop a brief list of information to be distributed to prospective purchasers. This sheet should include current taxes, utility costs and proximity of schools and transportation, as well as the best features of your house.

Determine the terms and conditions of your own mortgage. Contact your mortgage lender for this information. Also, a few days before you actually show your house, you should determine current mortgage market rates. Call at least two banks, two savings and loan associations, and two mortgage bankers for this information.

You should also purchase a mortgage guide listing the monthly payments for different loans at different rates under an amortization schedule. After all, most prospective purchasers will want to know their monthly costs.

Show your house. Many sales are made when open houses' are held on Saturday or Sunday. When you place your classified ad, tell the ad-taker you want it under the "open house" listings.

You might also want to consider showing your house "by appointment only." You can set your own pace and schedule prospective purchasers at your convenience. While this does not attract as many prospects, often it helps you screen the more serious purchasers.

And, don't bother to indicate "principals only." There is no way you can keep a real estate agent from inquiring about your house.

Obtain the necessary documents. Before you show your house, you will need some form contracts, to be prepared when that real purchaser shows an interest in your home. Most attorneys should be able to furnish you with copies of a real estate form contract. Additionally, the Bar Association of the District of Columbia (223-1480) sells form contracts for the District for a nominal price. If you are unfamiliar with this contract, consult your attorney or the Bar Assocition for guidance.

Make your house presentable. Step outside and look at it objectively. While you may not have to repaint, you should make your house as pleasant as possible. Take away the clutter that accumulates in every home. Put some of your furniture away to make your house look spacious and friendly. Open the windows and let the sunshine and fresh air in.

When prospective purchasers come to your door, introduce yourself and give them the fact sheet. Let them wander thourh your house without your "running commentary" about the virtues of each and every room. If buyers are interested, or have questions, they will get back to you.

Needless to say, this list is not all-inclusive, and you have a lot of homework before you can sell your house. But, it is possible, and you certainly should give yourself a chance. After all, there will always be plenty of real estate agents ready, willing and able to sell your house, if you decide to go that route.

Benny L. Kass is a Washington attorney. Write him in care of the real estate section, The Washington Post, 1150 15th St. NW, Washington 20071.