Wash or dry clean all clothes before you store them. Body oils can leave permanent stains and attract bugs. Rinse everything thoroughly. Detergent left in clothes can cause chemical changes in the fabric. Wash everything in soft water.
Hard water can cause yellowing and rust spots.
Never put clothes in plastic. Moth balls can stick to plastic and damage fabric. Plastic is airtight and clothes need to breathe. So you're better off using fabric. Old sheets and pillow cases are perfect for storing clothes.