If you pay your balance every month, you should be getting more than monthly bills from your credit cards.

You should be earning miles or points toward airline tickets, gift cards, electronic gadgets or even cash rebates.

Just look at how one consumer, Sabrina Karl, took control of her credit cards and made them work for her.

That's why we checked out dozens of cards to find the best rewards cards for you. We put them into two categories: air miles and cash back on gasoline purchases -- two of the most popular bonuses.

But beware that the rewards are not as generous as they used to be. Credit card issuers are raising rates, lowering credit limits and giving you fewer rewards than they did just a few months ago.

Our picks charge no annual fees. Some bestow extra miles, points or rebates on things you buy the most -- groceries, gas and pharmaceuticals. They also make it quick and easy to get a check or redeem the miles and points you've earned.

Interest rates weren't a big concern -- in fact, some of them are a little high.

But rewards cards make the most sense for consumers who pay their balances off every month. If you don't, you need a card with the lowest possible interest rate.

That said, here are our choices for the best reward cards:

Airline miles

None of the individual airline cards makes the cut. High fuel prices have forced carriers to offer fewer flights and reduce the number of seats available to frequent fliers, so it will be harder than ever to redeem the miles in those programs.

And from everything we've heard, it's pretty tough already. There are more miles needed for most flights and there are extra charges.

That's why we think the Capital One No Hassle Miles Rewards is your best bet.

Not only can you rack up miles, but you also get a 0% APR on purchases for one year. After that year is up, the rate will be a variable 13.9%.

If you have excellent credit, you can earn a hefty 1.25 miles for every dollar you spend on purchases. Those miles can be redeemed on any airline, with no blackout dates, no limit to the number of miles you can accumulate and no expiration date as long as you keep using the card. And there is no annual fee.

It's easy to figure out how many miles you'll need for airfare or a hotel stay. You just add two eros to the price of the purchase and that's how many miles you'll spend.

For example, tickets costing:

• $150 will require 15,000 miles.
• $350 will use up 35,000 miles.
• $350 to $600, you're charged 60,000 miles.

There is no limit as to how many miles you can spend or how expensive your ticket, hotel stay or cruise can be.

The reward system is flexible too, allowing you to redeem miles for merchandise, charitable donations, gift certificates or cash rebates.

If your credit is good but not quite good enough to land a No Hassle Miles card, consider the Miles by Discover Card.

You can travel on any airline with no blackout restrictions and get double miles for up to $3,000 in travel and restaurant purchases each year. Otherwise, you earn one mile for every dollar you charge.

In addition, you can earn 1,000 bonus miles each month you make a purchase during the first 12 months you have your card (12,000-mile cap). You also can use your miles for hotel stays, car rentals, cruises and other travel-related rewards.

If you don't use your miles, you can get gift cards to use for purchases at 50 brand-name partners' online stores or you can redeem them for cash.

Gas rewards cards

If you put in a lot of time behind the wheel and spend big bucks on gas every month, a little cash back might lessen the sting. We have two suggestions:

The Discover Open Road Card gives you a 5% Cashback Bonus on gas and auto maintenance purchases and up to 1% cash back on all other purchases. Discover also offers 5% to 20% cash back on purchases from their online retailers, but you're in this for the cash you can get for fill-ups.

In addition, there's an introductory rate of 0% on all purchases for up to 12 months, depending on credit. And when the 0% offer expires, your regular rate could come in at anywhere from 10.99% to 18.99%, once again, depending on your creditworthiness. However, fees are hefty, so avoid cash advances, late payments and exceeding your credit limit.

The Chase Freedom SM Credit Card offers 3% cash back on gas, groceries and fast food purchases for the first six months. After that, you will continue to receive 3% offers that will rotate quarterly. You earn 1% unlimited cash back on all your other purchases. No cap. No expiration.

In addition, you get a 0% introductory APR on purchases for up to 12 months, depending on your credit score. Chase has three pricing levels for all rates: elite, premium and standard for purchases, balance transfers and cash advances. And you can earn up to an additional 10% cash back at hundreds of merchants when you shop online with Chase Rewards Plus SM.

By Carolyn Siegel

Interest.com Associate Editor