State law puts the burden of proof on the property owner to show that the assessment is incorrect. Stating that property taxes are too high is not relevant. You should establish in your mind what you think your property is worth.
The best evidence that could be considered is a recent sale price of your property. The next best thing is recent sale prices of properties that are similar to yours in size, style, age and location. The closer in similarity and proximity, the better the evidence. Another type of evidence that is considered is a recent appraisal of your property.