Check your label. Yes, everyone always says that, but manufacturers don't attach garment tags for nothing. Following the label for washing instructions could mean the difference between keeping your sweet sweater around for many seasons or passing it off prematurely to your cousin--who happens to be in the second grade.
Turn your sweater inside out before washing it. This measure protect the fibers from "pilling," or creating tiny, tough-to-remove clumps. You can use a shaver on dry sweaters to remove the pilling later, but it's time-consuming, and you might not get it all. Save yourself this step now.
Hand-wash your cotton sweater in cool water and a mild detergent. Most cotton fabrics perform best in this setting because it is the gentlest method of washing, with little chance of shrinkage.
Remove your cotton sweater from the water and place it into a clean, thirsty towel. Roll the sweater up in the towel to remove excess water.
Remove the sweater from the damp towel and place it on a dry towel. Lay it flat in the shape you wish it to dry. Toss it into a cool dryer to fluff if you prefer, but don't use heat. Keep it in the dryer for just a few minutes, then remove it to air-dry it in its natural shape.
Make sure your sweater is thoroughly dry before you place it on a hanger. Severely pointed shoulders may be a look that works for Lady Gaga, but it makes your cotton sweaters look a mess--and not a hot one, either.