There are many websites promoting cheaper airline tickets. If you compare prices between the sites, and some sites even compare between other sites for you, you can find the best possible price. Many of the websites have a lowest price guarantee, so be sure to check the fine print in case you qualify for it.
Another way to save money is to request an e-ticket, instead of having traditional paper tickets delivered to you before the flight. They also have the safety feature of not being able to lose the tickets before the flight, especially if you book far in advance.
You can buy two “back-to back” cheaper round trip tickets instead of unrestricted tickets, which are more expensive. By using half of each set of round trip tickets, you save money. The major draw back to this is you can’t use them toward frequent flyer miles.
If you travel during the middle of the week, instead of over the weekend, you can usually purchase cheaper airline tickets. The weekends are higher volume, so seats are at a premium.