It’s no wonder that cash-back credit cards are the most popular kind of rewards card available. For doing very little, you get back money for every purchase you make.

To find out how much is at stake, we plugged the average expenses of an American household, according to the Bureau of Labor Statistics, into our new, Credit Card Adviser Comparison Tool. We found that between the best cash-back credit card and the worst that consumers would be likely to choose, the difference can be as much as $900 in how much cash you receive over the first three years that a card is being used.

Figuring out the right cash-back credit cards for your particular spending habits can be complicated. Some cards only provide 1 percent for all your expenses. Others provide more for specific kinds of expenses. For example, you can get credit cards that will give you 2 percent to 5 percent cash back on groceries or gas while giving you less for other purchases. You also need to take into account annual fees that may or not may be waived in the first year, and any special sign-on bonuses designed to entice you to apply for the card.

Top Picks

So what are the best cash-back credit cards for the average American family? The Credit Card Adviser Comparison Tool suggests the American Express Blue Cash Preferred card, which pays back the most—6 percent on the first $6,000 in groceries each year, 3 percent on gas, and 1 percent on all other purchases. The total cash you would get would be $547 in the first year of card ownership and $1,340 in the first three years. Note that the card charges a $75 annual fee (any fees are accounted for in our calculations).

The three runner-ups provide $1,207 over the first three years. The Citi Double Cash Card and the Fidelity Rewards Visa Signature, each pay 2 percent. The Discover it Miles card pays 1.5 percent on all purchases and offers a generous first year bonus. None charge an annual fee.

Maximize Your Cash Back

Depending on how much you charge to your cards, you could get significantly more back.

To use the Credit Card Adviser Comparison Tool, input your monthly spending in five different categories—gas, groceries, travel, restaurants, and other expenses. It will tell you the cards that will give you the most over a period of one year and three years after taking into account annual fees and sign-up bonuses.

You may find that you should apply for more than one cash-back credit card. That way, you can maximize the cash you receive by carefully charging your purchases to specific credit cards, suggests Brian Kelly, founder and CEO of The Points Guy, a travel and credit card blog.

Kelly says you could use a card that pays 5 percent on gas exclusively for your fuel purchases. If that card provides minimal cash back for, say restaurant expenses, use a different card —perhaps one that pays back 3 percent.

Once you have the cash-back cards, make sure you are charging the right expenses to the right card. You can keep track of your cash-back cards with an app, such as the TPG To Go app, available for Android phones and iPhones.

Finally, to really benefit from these cards, pay off your balance in full each month. If you don't, the finance charges that come with carrying a balance can wipe out the benefits, says Michael Saccucci, director of statistics at Consumer Reports.

Update: Please note that the Credit Card Comparison Advisor Tool is not currently available.