I keep my order confirmations and shipping notifications in a folder in my email account. When the item arrives, I check to see that nothing has been backordered. If everything is there, then the email is deleted. If it's not, I keep the email "live".
One thing - use your credit card for orders, not your debit card. There are fewer protections for debit cards and your account balance could be totally wiped out. With credit cards you're only liable for the first $50.