The tax assessment authority's office -- or its website -- is a good place to find comps. A website operated by a local multiple-listing service (such as Realtor.com on MSN Real Estate) also may be a good resource. Keep in mind that some sites may be incomplete or contain outdated or erroneous information. A search of several databases, based on the parameters of your home, should turn up some useful results.

Appeal can take months

The property tax appeals process can take place at multiple levels, such as a written form or request for a review, a citizens' panel, an assessment appeals board or other forums. Each level will have its own rules, guidelines and deadlines, set by law or the tax authority.

The first opportunity may be a chat with the local assessor, while the last resort could be a full-blown lawsuit, according to Bruce Woodzell, the president of the International Association of Assessing Officers in Charlottesville, Va.

How long the entire process will take depends on local resources. In some places, homeowners receive a final resolution within a few months. Elsewhere, an appeal can take a year or longer.

The process is data-driven, so homeowners should avoid emotional arguments. Assessors generally have "no connection whatsoever" to setting property tax rates or collecting property taxes, so going in angry or pleading for a reduction is unlikely to succeed, Brusniak says.

"Information speaks volumes," Woodzell adds. "If you have hard facts, if you have sales data, and if you have all your information right, it really helps."

Some jurisdictions offer a tax break if you occupy your home as a principal residence, are elderly or disabled, or meet other qualifications. Generally, you must be proactive to claim these benefits, Brusniak says, so call the assessor's office and ask. Again, a missed deadline may very well mean no tax break for that year.

Do-it-yourself project

Most homeowners can contest their property taxes on their own, or perhaps with some help from a local realty broker. Only rarely is an attorney or private appraiser necessary to the process.

"For the most part, this is a thing you can do yourself," Brusniak says. "If you have a $5 million property that's a really complex issue, then perhaps you ought to bring in an attorney who can help you."

The possibility that an appeal could trigger a higher valuation might spook some homeowners, but Brusniak suggests the risk is small.

"Can it happen?" he says. "Yes. Does it happen? Rarely. Generally that's when there has actually been a valuation error."