For the best baking experience always use parchment paper on your cookie sheets (cut to fot don't let it hang over edges) this helps prevent over browning and sticking.
The thicker the cookie sheet the better it will conduct heat more evenly.
Try not to use dark colored sheets or non-stick. The dark color promotes browning quickly and the non-stick will dry out your cookies as they bake.
A matte finish is better than a shinny finish and a smooth surface is better than a textured one.
Avoid cookie sheets with four sides, this will effect the edges of your cookies as they bake. The best is a cookie sheet with two handles located on the short ends of the sheet.
The Holy Grail of cookie sheets is made by Vollrath Co. it is a little pricey but will last you forever with perfect results.
