The next step should be to start comparing fares from a number of different sources. Unfortunately, there is no one place—online or off-line—that will always have the lowest fares. Because airlines negotiate exclusive deals with different travel websites, you'll need to shop around and compare prices. In addition, some airlines' fares can only be found at their own websites, including Southwest, so be sure to check on airline websites, too.

Here are a few of the best places to look for deals:

Airline websites: Airlines often provide incentives for booking airfare directly through their own websites. Some airlines let you search for a list of all fares that are on sale from your home city. And, in most cases, you can book directly from the airline's home page.

Online travel agencies: You can also check for deals at the three largest online travel companies: Travelocity, Expedia, and Orbitz. Each of these sites uses a slightly different reservations system, so you may find different prices depending on which one you use.

Our price-comparison tool allows users to enter a travel itinierary once and search dozens of travel providers, including the online travel agencies and both major and low-fare airlines.

Consolidators: These companies buy tickets directly from airlines at a discount, and re-sell them to consumers. You can sometimes get bargains with consolidators that you can't find anywhere else. The travel section of your local Sunday newspaper will often have ads from consolidators in your area. However, be sure to learn about a consolidator company to make sure it is legitimate before you purchase tickets. It's also a good idea to use a credit card to protect yourself.

When looking for deals online, be very careful to note whether or not the fares include all taxes and fees. On most domestic flights, these additional charges can total up to $40, and on international flights, up to $200 or more.

Learn how additional taxes and fees increase your airfare.