Most cookies freeze well. (Meringues do not). My colleague Carole Walter, a James Beard award winning baker, recommends layering cookies with sheets of wax paper in airtight containers. Wrap the container in foil and slide it into a plastic bag to make it even more airtight. The less air that gets in the package, the "fresher" the cookies will stay. Cookies can often retain their flavor and texture for up to 6 months.
Carole refreshes thawed cookies on a baking sheet in a 325F for anywhere from 5 minutes to 10, depending on the size and texture of the cookie.
See Bake-and-Freeze Cookies for make-ahead cookie recipes.
Recipe: Frosted Sugar-'n'-Spice Cookies