Sleeping bags take a particular beating because they're mostly used outdoors. Here are some things you can do to keep them in good shape:
Pre-treat spots and stains on the bag cover with liquid detergent.
Wash down-filled sleeping bags in cool water with mild detergent.
Wash polyester-filled sleeping bags in warm water with an all-purpose detergent.
If your sleeping bag can be machine-dried, tumble it with a clean, dry tennis shoe to prevent matting and a clean, dry bath towel to absorb excess moisture.
If you line-dry the sleeping bag, unzip it before drying.