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 the first year. After that year is up, the rate will be a variable 13.9%. And you need excellent credit to qualify.

You earn one mile for every dollar you spend on purchases up to $1,000 per billing cycle. After that, you earn two miles for each dollar spent.

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 zeros 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 that 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.

Your annual interest rate is 0% for the first six months, and that also applies to balance transfers made with your application. After that your credit history will be reviewed and your rate will fall between 11.99% and 18.99%.

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.

Merchandise rewards cards

The Citi Forward Card rewards you in two ways: it allows you to lower your interest rate, it helps you build points faster and it offers 0% financing on purchases and balance transfers for six months.

You can reduce your purchase APR by as much as 2%. All you have to do is make on-time payments for three straight billing periods, keep your balance below your credit limit and your APR will fall by 0.25%. You can do this eight times, so your starting APR of 14.24% could become 12.24%.

The Citi Forward Card is also generous with points, which allow you to buy merchandise, travel and more through its ThankYou Network.

You can earn 100 bonus points each time you make an on-time payment and stay under your credit limit up to a maximum of 6,000 points.

You also can earn 6,000 bonus points by making $50 worth of purchases during the first three months of card ownership. And you get another 5,000 points if you sign up for paperless statements within three months of account opening.

Money spent on books, movies, music and restaurants will earn you five reward points for every dollar spent, and you will receive one point for every dollar you spend on other purchases.

By Carolyn Siegel

Interest.com Associate Editor