I've recently written a couple of articles that discuss some of the easy ways that people can get a free plane ticket. The first focuses mainly upon how people can earn frequent flyer miles and talks about credit card bonuses, search bars, and online shopping portals. The Top 5 Ways to Earn Frequent Flyer Miles probably includes most of the most common methods, but it should be able to teach people some good tricks to try.
The second article on How to Get Cheap Airfare talks about frequent flyer miles, but it also discusses some alternate ways to get a free or discounted ticket. By using a variety of methods, there is little reason to pay the full price on a legacy airline for a flight.