The easiest way to store old dance costumes is to hang them on sturdy hangers in a sealed garment bag. This will keep the costumes looking neat and organized while also protecting them from dust and other damage. If you have multiple costumes, you can use clear plastic bins with lids to hold them. Make sure you label the bins so you know what costume is inside each one. If you don't have room to hang the costumes, you can fold them neatly and store them in a labeled box. Keeping them in a cool, dry place will help them last longer and stay in better condition.