Possible problems

I used to have the same problem. If you're using margarine switch to butter, there's too much water in margarine. If you can get one, I would recommend getting a baking stone. If you use an aluminum pan use parchment paper on it. What temperature are you baking at? Sometimes it helps to bake a little longer at a lower temperature. Also, maybe you need a little more flour, by the way, you aren't using self-rising flour are you? I wouldn't recommend that for cookies.