Go to the American Airlines site and visit the “Register For A Chance To Win A Trip To New York City – John Legend & The Roots Wake Up! Concert Series” sweepstakes. Register for the sweepstakes and then purchase a flight on AA.com by September 30, 2010 to be entered for a chance to win. You can also enter the contest without making a purchase by registering here.
You can check on the rules (Blah, blah blah, no purchase necessary; blah blah, void where prohibited) here.