Keep a plastic baggie, folder or envelope for clothing receipts and tags. I've often found that I like clothing and would like to purchase more in a different color but can't remember where I purchased them. Also, by keeping the tag you can take it with you to make sure you find the same item. When returning clothing the tag and receipt help you to get an accurate refund. If the item is on sale when you return it you may only get the sale price without the receipt.
Note: I keep all receipts for a year and if they are for a large item or appliance, I attach the receipt to the instructions and keep both in a folder.