I use butter and eggs right out of the refrigerator so the dough stays cool and the cookies maintain their thickness during baking; I also use ungreased cookie sheets. To keep the cookies soft and chewy, store them in an airtight container along with a slice of bread.
I modified Beatrice's Excellent Oatmeal cookies very slightly. I came up with something that my boyfriend went CRAZY over! I've never seen him enjoy cookies to that extent! He said I blew his mother's recipe away.