If you feel your property has been overassessed, you can appeal to your county's tax assessor office. Google your county's assessor's office to find the website and call them directly to inquire about the appeals process. Be prepared to provide concrete reasoning for why you feel your taxes are too high (i.e., your neighbor has a similar property and his taxes are much lower, the property's market value has gone down (you may need to have your home appraised) and needs to be reassessed, you are not receiving certain exemptions, etc.).
There are real estate attorney's who specialize in aiding people in reducing their property taxes, as well, although their services are not free. However, if you feel strongly that you are paying too much, hiring an attorney to help you navigate the bureaucracy might be worth your while.