As we reach the height of summer, Americans are getting more and more restless. Increased travel costs due to high oil prices have dampened (or outright destroyed) the travel plans of drivers and airline passengers alike. No matter how you plan to get to your destination, the secret to cutting your costs lies in using your credit cards.

TUTORIAL: Credit Cards: What Are Credit Cards?

1. Use Cash Back Cards for Gas
Every time gas prices rise, we see a rash of stories on how to save money at the pump. The one piece of advice that is rarely mentioned is probably the easiest way to save on every single tank. By choosing one of the best gas credit cards, drivers can save up to 5% on every fill up. Just be careful to closely note the terms and conditions of each offer as many of these exclude warehouse stores like Costco from their highest discounts. (For related reading, see 4 Tips For Using Credit Cards Overseas.)

2. Use Sign Up Bonuses to Earn Frequent Flyer Miles
If you travel on business, you probably have no shortage of frequent flyer miles. Likewise, if you make a lot of money and use a mileage earning credit card as your primary method of payment, you should also be flush with miles. For the rest of us, there is always a credit card sign-up bonus to catapult our frequent flyer accounts towards an award.

The key is to only apply for credit cards when there is an exceptional promotion. Just about any card will give you 25,000 miles, which is enough for a domestic round trip ticket at the lowest redemption levels, but that is really just the beginning. Recently, the British Airways card from Chase had a promotion where they were offering 100,000 miles as a sign up bonus. While this promotion is now expired, the Chase Sapphire card was offering 50,000 points and there are reports of some people receiving targeted offers of 100,000. These points can be redeemed for miles with United/Continental or British Airways. (For related reading, see Credit Card Perks You Never Knew You Had.)

3. Take Advantage of Airline Mergers
Another trick to increase the amount of bonus miles you receive is to earn a sign-up bonus from two airlines that are about to merge. Currently, one could earn bonuses from merger partners United and Continental, as well as Airtran and Southwest, even if you already have a card from the other carrier in the merger. In both of these situations, it is only a matter of time until the mergers complete and all of your accumulated points are pooled into one account.

4. Leverage Non-Mileage Perks
Today, many of the best travel rewards credit cards also offer baggage fee waivers, priority boarding, and even business lounge passes. The Delta SkyMiles Gold card, for instance, offers one free checked bag for up to nine people traveling on the same itinerary.

However, the more perks you receive, the higher the annual fee will be, so make sure you find it worthwhile. (For related reading, see Watch Out For Changes In Credit Card Agreements.)

5. Use a Flexible Rewards Card
Loyalty programs lock you into using one particular airline. Unfortunately, once you are ready to redeem them, your airline may not have any award seats available for a reasonable amount of mileage.

You can have your cake and eat it too by switching to a credit card that allows you to exchange points for miles in many different programs. American Express's Membership Rewards, for example, allows its points to be converted into miles with over a dozen airlines. The American Express Starwood Preferred Guest card is even more flexible - points can be exchanged for miles with 29 different airlines around the world.

What is even more amazing is that when you redeem 20,000 Starpoints for miles, they give you an additional 5,000 point bonus. You could actually earn miles faster with this card than you could with most airline affiliated cards. When you consider all of the partner awards available from each of those airlines, one could earn free travel to virtually any place on earth.

TUTORIAL: Choosing A Credit Card

6. Don't Forget Hotel Cards
Hotel programs can actually be a better value that frequent flyer miles in some cases. Points earned in the Starwood program, for example, can be redeemed for hotel stays with no capacity restrictions or blackouts, as do the ICH group and Hilton reward programs.

The Marriott and Hyatt programs claim no blackout dates, however many popular dates will be unavailable due to capacity controls. People who are not frequent travelers can do well by racking up hotel points with their credit card and redeeming them for vacation stays. Combining airline awards with free hotel stays yields an extremely low-cost vacation.

7. Save Money on Currency Conversion
If you'll be crossing the border for international travel, your credit card can save you money or cost you dearly, depending on how you use it. Most credit cards charge a foreign transaction fee of 1-3%, but savvy travelers can find credit cards without this fee.

When you use a card without a foreign transaction fee, you actually get a very competitive exchange rate on all of your purchases. The worst thing you can do, though, is use your credit card to withdraw cash. Do that and you will likely be hit with a cash advance fee and a higher APR, along with any foreign transaction fees charged. (For more, see APR and APY: Why Your Bank Hopes You Can't Tell The Difference.)

The Bottom Line
Finally, when you travel, keep some of your cards on you while leaving others in a separate, secure place. That way, you'll know that you'll be able to make purchases should either location be compromised. By choosing the right card to save money on travel, you can more easily justify going somewhere fun this year for vacation. (For related reading, see How To Dispute A Credit Card Charge.)