Wouldn't it be great if you could have a single credit card that gave you the best rewards for everything? Unfortunately, that sentiment seems to be a pipe dream, as credit card companies are doing everything they can to carve out narrow niches that give you maximum cash back only on very limited items.

Should you pay for rewards?
In the latest move in the card industry, American Express (NYSE: AXP) has made some major changes to its Blue Cash card. Blue Cash, which had no annual fee, has been particularly popular among those who spend a lot on their credit cards, because until now, the card offered a 5% rebate on gas as well as purchases at grocery stores and drug stores -- but only after you had already made at least $6,500 in annual purchases with the card.

With the changes, however, cardholders have a choice of two cards. One card, dubbed Everyday, gives 3% cash back at grocery stores, 2% at gas stations and department stores, and 1% on other purchases. This card comes with no annual fee.

The other card, called Preferred, has a $75 annual fee. But in exchange for the higher cost, the Preferred card gives enhanced rewards. Cardholders get 6% on groceries and 3% at gas stations and department stores, with 1% still applying to other purchases.

A big juggling act
The challenge in trying to manage your credit cards to make the most of available rewards is in navigating all the moving targets. Although American Express appears to be keeping its rewards stable with its new Blue Cash card, many issuers make things a lot more complicated. Citigroup (NYSE: C), Discover Financial (NYSE: DFS), and JPMorgan Chase (NYSE: JPM) all have card reward programs that have rotating categories each quarter. So for instance, in one quarter, a card may give you a 5% reward for purchases at grocery stores; but the next, that reward may drop to 1% while another category, such as home improvement store spending, moves up to 5%.

Such programs add enormous complexity -- and hassle. Typically, you have to track your spending, because they usually include limitations on how much you can spend that qualifies for the higher reward amount. Moreover, you often have to enroll for each quarterly program separately -- with no option for automatic enrollment. Forget to sign up, and you can kiss those extra rewards goodbye. And finally, if the store where you shop somehow gets miscategorized, your credit card company may not recognize your purchases as qualifying for the bonus reward amount.

At least they're still paying rewards
Nevertheless, as difficult as it is to navigate some rewards programs, they still represent found money for customers. And with banks struggling to find ways to make back lost revenues from credit card reform and limitations on interchange fees for debit cards, card issuers including Wells Fargo (NYSE: WFC) and SunTrust (NYSE: STI) have stopped offering rewards entirely on debit-card purchases.

As for the dilemma raised by increased rewards in exchange for an annual fee, AmEx isn't the first company to force cardholders to consider that issue. Capital One (NYSE: COF) pitched a card last year that offered double rewards miles for those willing to pay a $59 annual fee. In the end, whether it makes sense to pay up for extra rewards is a simple cost-benefit question: Will you earn more in rewards than you pay in annual fees? If you track your credit card purchases -- or have access to old statements to go back and review them -- then it should be fairly easy to do the math and come up with the right answer.

Be a smart cardholder
While many credit card users struggle under mounds of debt, responsible cardholders have access to just about any card they want. The rewards game may be getting more complicated, but it's also more lucrative for those willing to figure out the rules.

Want to more about making the most of your good credit? Check out the Fool's Credit Center and get more great tips on how to manage and improve your credit.

Fool contributor Dan Caplinger always stops for free money. He doesn't own shares of the companies mentioned in this article. American Express and Discover Financial Services are Motley Fool Inside Value picks. The Fool owns shares of JPMorgan Chase and Wells Fargo. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Fool's disclosure policy is always rewarding.