Old thread, but since it's been bumped, I'll add our cash back routine:
For gas, groceries and drug stores, we get 5% using the AMEX Blue Cash. We're grandfathered on an older version with no annual fee. For everything else, we get 2% using the Fidelity AMEX. And for any merchant who does not accept AMEX, we get 1.5-2.0% using the Fidelity VISA. DW is well-trained on this routine.
Also... there is a fairly well-documented method to get 12% using the AMEX Blue Cash card to buy gift cards at Kroger. You get 5% immediately from AMEX for the "grocery" purchase. Then, Kroger gives 2X fuel points on all gift card purchases. The resulting discount at the pump is equal to an additional 7% off the original gift card purchase. Total discount = 12%.
Just last week, I saved $120 on a $1,000 purchase at Best Buy using this method. Also, all my Amazon purchases last Christmas were made with gift cards I purchased at Kroger with the AMEX card.
There is a newer version of the AMEX Blue Cash that pays 6% on groceries, but it has a $75 annual fee and a $6K cap on "grocery" purchases. So I stayed with my older card which has no annual fee, no "grocery" cap, but pays a slightly lower 5%.
Retired at 52 in July 2013. On to better things...
AA: 45% stock, 35% bonds, 15% real estate, 5% cash