How do you keep track of all your credit cards and their benefits?

First off, I have excellent credit and never pay for a card. Ever! If there is an annual fee or a use fee, that card is dropped immediately. Second, I always pay the bill off completely so interest rates are not a concern. With that background info, here’s my question.
I have at least 6 cards, all with varying benefits. 2% on gas, 5% on medications, 1% on everything, 2% on groceries, 3% on gas, 5% at home stores, and in every combination you can imagine.
How do you keep track of which card is the best one to use? Do you carry all the cards with you? Do you just remember all the benefits? Do you pick one card and just use it?
I have actually started writing the benefits right on the cards in black marker. What do you do?