A rising property tax assessment can seem flattering in a robust real estate market. Wow, my home is worth that much? But in a slow or declining market, paying more property tax feels like adding insult to injury. Even though local property taxes fund important services like education, no one wants to overpay.

That’s why requests for reassessments are increasing across the country. In Los Angeles County, some 1,800 homeowners asked for reassessments in 2007, compared to about 500 in a typical year. “The process is on a par with contesting an unfair or inaccurate traffic ticket,” says Pete Sepp, vice president of policy and communications for the National Taxpayers Union, which advocates for tax reform. “You need to have evidence, logic and confidence that justice will be served.” If you’re considering contesting your assessment, here are three do’s and three don’ts to help ensure success.

Do:

1. Understand the rules

Property is assessed on regular cycles, such as every one, three or five years. Assessment information is mailed to homeowners annually, before the tax bill is due. Check with the Assessor’s Office in your county to understand the timeline, as well as the deadline to appeal an assessment.

Successful appeals can be made on two grounds: accuracy and fairness. Your assessment is inaccurate if it contains a factual error or a false assumption. Your assessment is unfair if it was assessed at a higher rate than comparable homes or above fair market value.

2. Research before you proceed

Examine the statement you receive from the assessor. Do you have two bedrooms, not three, or is the square footage overestimated? Both of those obvious mistakes could qualify you for a reduction.

If you suspect unfairness, you’ll need to do some legwork to prove it. You could hire an appraiser to conduct an independent assessment or collect comparable assessments from homes in your neighborhood to show that yours is high in relation to them. “You might find that on a cost-per-square-foot basis, your home is assessed 25 percent higher than other ranch-style, 20-year-old homes in your neighborhood,” Sepp says. Or, your home may be assessed at the same rate as your neighbors’, but yours is next to a freeway ramp. In fairness, its assessment should be lower. Assessments can be requested through the Assessor’s Office, though you may need to file a formal notice of appeal.

3. Take one step at a time

Once you’ve gathered your facts, call the Assessor’s Office and request an informal meeting. Many times a straightforward correction can be easily handled over the phone or in a casual meeting if you provide proof of the error. Pursue this approach before requesting a hearing before the assessor’s appeals board, which will be a more formal setting. Either way, you don’t need an attorney unless your case is very complicated or odd.

Don’t:

1. Be afraid to ask

“If you don’t ask, you’ll never get a tax reduction. If you believe your value is lower, you have to ask,” says George Relias, an attorney with Fisk, Kart, Katz & Regan, a Chicago law firm and founding member of the American Property Tax Counsel. In the current real estate climate, you might be right.

2. Have unrealistic expectations

You may have to decide how far to take your protest. If you can’t settle with the assessor, an appeals board will hear your case. Still unhappy? You can appeal to a higher level such as state court. But remember that even a partial reduction in your assessment will bring a lower tax bill. The extra time and cost to keep fighting may not pay off.

3. Lose your focus

Get your facts straight, and stick to the facts when making your case. Also, don’t confuse what you’re fighting for, which is a reduction in your assessment, not a change in the tax you must pay. “You’re contesting the value of your home, not the tax itself,” Relias points out. “The taxes are the tail that wags the dog.”