Ok for the truly nerdy, did you know that if you sign up for earny.co it will track your purchases and if you have a chase or Citibank card, it will take a 25% commission, but will automatically handle the refund process. A pretty good deal.
If you want to do it manually, then Chase, Discover and Citibank all have this. Citibank is the best (so maybe a good card to use) for this. It has something called Rewind which does this automatically.
then if you are careful, most cards from Merrill Lynch to Chase Sapphire will also double the manufacturer’s warranty. You need to register the warranty with Visa to make this all work at cardbenefitservices.com