Thin and Crispy
Use all granulated white sugar. If a recipe calls for brown and white sugars, substitute an equal amount of white for the brown. White sugar helps absorb moisture in the dough, resulting in crisper cookies. And as it heats and dissolves, it causes the cookies to thin out.
Thick and Moist
Use all brown sugar (the reverse of thin and crispy). Brown sugar contains molasses, which adds moisture to the cookies. Molasses is also slightly acidic, which causes the proteins in the dough to firm up quickly instead of spreading out.
Soft With Crisp Edges
Stick to equal parts granulated white sugar and brown sugar. The granulated sugar causes just enough spread for the edges to firm up, while the brown sugar softens the middle for that irresistible chew.