A central question in every real estate transaction is: Just how much should you pay?

Real estate values are established at the instant when a buyer and seller agree on a specific price. At any other time, or with any other buyers and sellers, the value could be different.

While all real estate sales are independent of one another, current pricing is certainly influenced by such factors as past sales in the neighborhood, the availability of other properties, time on the market, the cost and availability of mortgage money, the economic needs of buyers and sellers, and the negotiating skills of both parties.

To check past sales, consult the Lusk Reports which are available at libraries or through many brokers. This service is an up-to-date listing of actual sales on a street-by-street basis.

Both multiple listing service and newspaper advertising are useful guides to currently available properties. However, these information sources only show prices prior to negotiation and do not represent a complete inventory of homes on the market.

While information sources are helpful there is no substitute for actually visiting homes in a given neighborhood. Open houses, usually on Sundays, enable buyers to physically inspect individual properties. This can be an enlightening experience.

In one case a house was advertised as having five bedrooms and a very reasonable price. Upon inspection it was found that the property did indeed have the advertised number of bedrooms -- two of which had been carved out of the living room.

When looking at different properties keep records of what you see. How do the homes compare? Check the construction of the property, style, number of baths and bedrooms, the condition of the kitchen, special features such as a full basement or storm windows, and other factors which you feel are important.

Over a period of time you will develop a sense of values. You will also see that all houses represent a package of benefits and faults. How much more would you be willing to pay for a modernized kitchen? How much less would you offer for a property with three bedrooms rather than four? These questions and others will help develop your bargaining posture.

Buyers should regard the purchase of a home as a business transaction. The best way to enhance your negotiating position is to examine and understand the choices in the marketplace. Certainly an informed buyer would do as much when purchasing a car or major appliance, so why not a home?

Peter G. Miller, a broker, teaches the course, "How to Sell Your Home -- With or Without a Broker," through the Consumer Real Estate Center in Washington.