I use a few different credit cards to maximize my cash back and other rewards. If I sign up for a "points" or "miles" card, I usually get one where I can easily redeem my points for gift cards that are nearly as good as cash (e.g. gas gift cards).
For example, I've got one card for 5% cash back at gas stations, another card for 5% points at restaurants and entertainment, and third card for 3% at grocery stores, utilities, and some other categories.
It's hard to recommend the best card for you without knowing the categories in which you spend the most, but some good cards are the AmEx Blue Cash, Citi Diamond Rewards, Capital One No Hassle Miles Ultra for Professionals, Capital One No Hassle Miles for Travel and Gas, etc.
You can use the rewards calculator linked-to in my signature to help figure out which card or combination of cards would pay you the most in rewards for your normal spending profile.