When a home buyer makes a small or zero down payment, the appraisal is vital to obtaining a high loan-to-value ratio mortgage. However, if a home buyer makes a large down payment, then the appraised valuation to confirm the sales price is not so critical.

WHAT IS AN APPRAISAL? A state-licensed appraiser makes professional real estate appraisals. Any other evaluation, such as a real estate agent's estimate of market value, is not an appraisal, but rather an opinion of market value.

An appraisal of real estate market value is an estimate by a trained appraiser of the most likely price at which a property will change ownership, with neither the buyer nor seller being under pressure to buy or sell.

But the real world is much different. There are different types of appraisals, such as a "quick sale value," "as-is condition," "future renovated valuation," and others. The skill and experience of the licensed appraiser play a key role in the accuracy of the appraisal.

Until there is an actual property sale, an appraisal is just an estimate of probable market value. However, even when there is a sale, the buyer might have overpaid or a desperate seller might have accepted a below-market purchase offer.

IS APPRAISAL AN ART OR A SCIENCE? During the last 10 years, there have been many attempts to make real estate appraisals more accurate, especially with automated valuation models (AVMs). Mortgage lenders would be thrilled to be able to verify the exact market value of a house by pressing a few buttons on a computer. Although that day might be coming, it has not yet arrived.

The latest attempt to eliminate the need for appraisers is the free Web site www.Zillow.com, which claims to have 60 million U.S. homes profiled. For several of my properties I checked, I found the results amazingly accurate. I especially like the aerial views with the lot boundaries superimposed.

Then I checked the house where I grew up in Edina, Minn. Zillow reports a one-bedroom, one-bathroom house worth $1.2 million. That house description sounds like a shack. If the valuation is correct, I wish my parents hadn't sold that house. The reality is it is a very nice three-bedroom, two-bathroom house. Zillow isn't always correct.

However, when houses and condos are relatively similar to nearby houses, AVMs can be very valuable to help estimate market values. But appraisers will always be needed to verify valuations, especially in neighborhoods of unique one-of-a-kind homes.

Although computers have changed real estate appraisals, there is no substitute for the experience of a realty appraiser to interpret the recent sales prices of comparable nearby houses and condos, which determine the market value of a specific home. Equally important, an expert appraiser is needed to evaluate if the local home sales prices are rising, falling, or "normal." So far, computers haven't been able to replace this judgment test.

HOW TO GET AN ACCURATE APPRAISAL OF YOUR HOUSE OR CONDO. The Internet can be used to research approximate market values of houses and condos, based on recent sales prices of similar neighborhood homes within the last six months.

But that is just a starting point because each residence is unique. Market value depends on many variables. However, there are still a few basic rules to assure an accurate appraisal:

1.) GET THE HOME INTO TIP-TOP CONDITION. If you are buying a house or condo, the seller has presumably made the residence look its best. However, if you own the home and need an appraisal for mortgage refinancing or other purpose, aim to put the home into its best "model home" condition before the appraiser arrives.

Because appraisers often inspect three or more houses each day, and can't possibly remember each home's special features, it is best to hand the appraiser a list of the residence's special features, especially those that add market value. Also, if you know of recent nearby home sales prices, be sure to hand that information to the appraiser.

A Realtor friend of mine, who never has problems getting an appraisal to match the home's sales price, tells me, "I practically do the entire appraisal to be sure the house appraises for the sales price."

2.) ALWAYS ACCOMPANY THE APPRAISER. Either the real estate agent or the homeowner should always accompany the appraiser to facilitate the inspection and answer the appraiser's questions. Be sure to point out the home's special features and benefits that the appraiser might miss during the inspection.

3.) INSIST THE LENDER WILL PROMPTLY PROVIDE THE BORROWER WITH A COPY OF THE APPRAISAL. Technically, the appraisal belongs to the mortgage lender who hired the appraiser, even when the homeowner or home buyer is paying for the appraisal.

Borrowers should insist their lender agrees to promptly provide the borrower with a copy of the appraisal. If the appraisal comes in low, the home buyer, realty agent, and homeowner should have immediate access to that appraisal to correct any errors.

For example, when I refinanced my home last year with Wells Fargo Mortgage, I was very impressed when the lender sent me an overnight FedEx copy of the appraisal.

If the appraisal comes in low, and you see the appraiser made an error evaluating your house or condo, don't hesitate to promptly request a correction or a "review appraisal" by another appraiser (to be paid for by the lender).

CONCLUSION: Although appraisal is still very much an art, rather than an exact science, computers continue to help make residence value estimates more accurate. However, licensed appraisers will always be needed to verify the facts and use them to arrive at expert valuations. More details are in my new special report, "How to Get the Best Appraisal of Your House or Condo," available for $5 from Robert Bruss, 251 Park Road, Burlingame, CA 94010 or by credit card at 1-800-736-1736 or instant Internet delivery at www.BobBruss.com.