Dif requirements for dif states/counties. Find out the requirements. I can tell you that often you have to get the right appeal form and submitt it with at least 3 sales in the area for similar dwellings. These sales have to be within a certain distance of your property and sold within a required time frame. Then file the appeal and two things could happen. 1. You could get a call from the office and get an offer; and 2. You might be given a court date and the opportunity to present your case. In the case of 1, you might still get a court date but you can ignore it if you have accepted an offer. You may also have to wait, continue to pay the current taxes and eventually get an "over payment" refund check...THEN your your next tax bill will reflect the change. A cumbersome process but you don't gat something for nothing and last time I did it, it saved me $2k.
BTW, make sure that properties near you are not the same or higher, for that should that be the case, it may back fire and you may be subject to a re-assessment that will give you an increase instead.