Once a month go through all of your drawers and closets for discards. Put discards in a box for donation or to sell at a garage sale. If for a garage sale, make sure you price things as you pack them. It will make your sale much easier.
As a general rule get rid of anything you haven't worn for a year, unless due to pregnancy or prolonged illness. You probably won't ever wear them again. And by the time you can they won't be in style, or your style.