Going through my to-be-filed box of papers to get ready for taxes :x I came across a page of notes I'd made from Alton Brown's show on cookie baking. I thought I'd pass them along, in case they can be of help to you.
Increasing the amount of baking soda results in a thinner cookie.
Replacing one or more eggs with milk will cause the cookies to spread.
A higher ratio of white to brown sugar will result in a crispier cookie.
The ideal sized scoop for cookies is the #20, which holds 1.5 ounces of dough. (Only Alton would think to tell you that, LOL.)