Money Magazine came up with a list of things you can do to get the freebies.
First, check to see if your airline has a dining program. That would allow you to earn miles by spending for a meal at one of the qualifying restaurants. For example, United Airlines gives out 1,000 free miles for the first $50 you spend dining out. Just sign up for its "Dining for Miles" program online or by phone.
Next, check out social networking sites and download airline apps. If you "follow" or "like" an airline, you might get rewarded. Money Magazine says Hawaiian Airlines is doling out 500 free miles just for following it on Twitter and Delta gave 1,000 free miles this summer for anyone who checked in using its mobile app.
Finally, some programs give out miles when you pay your bill at hotels and rental car outlets. Starwood, which owns Sheraton, Westin and "W" hotels, is offering 1,000 Southwest points for stays through December 15.
Remember, though, you can't earn any points if you're not a part of the program so sign up next time you book a flight. Nearly all frequent flier programs are free of charge.