If you are looking for a cross country flight, your best bet is Southwest Airlines. This airline is the only one in the pack that doesn't charge a second bag fee, isn't charging to sit on an isle and actually is a quite popular American airlines. Considering that Southwest Airlines Flights are already the lowest of the airlines, it is still possible to get a ticket cheaper. Here's how!
Find yourself a green buddy pass. These aren't hard to find during off month and can be used on any flight. Buddy passes are given to employees as bonuses for friends and families to travel on. Since the employee themselves gets significantly reduced rates and not everyone wants to take their family on a trip, employees sell these buddy passes online. You will find them in the Travel Section of Craigslist. Also, if you know a Southwest employee, ask if you can buy one from them.
Buy a discounted gift certificate or free travel pass on eBay. These are legitimate tickets and certificates that are sold because the current holder doesn't want them Since they aren't used and are not in the form of a travel ticket, it can be redeemed for you to travel on. Arrangements like this are all the rage on EBay with good deals to boot.
Sign up for the ezine that is sent out to customers who request it. This is a sporadic email that comes every couple months, but when it does you will find great deals (depending on your destination) and information.
Watch the local newspaper and Sunday Night Football. Using advertising strategically, Southwest Airlines advertises lower flight deals to everyone at the same time. Meaning get on their website and get those deals first!!!
Give yourself plenty of time to buy a ticket and look for good deals!