Check the minimum number of miles required to gain a free flight. Some airlines have award travel starting at 25,000 miles, while it takes up to 50,000 miles for competing frequent flier members.
Most frequent flier award programs are linked to other travel services like hotels and car rentals. Compare the other ways in which you can spend and accumulate miles if you use one of these travel services more than flying.
Most airlines belong to regional and international networks whereby they are partnered with other airlines to serve a greater area. Consider the partner airlines, where they fly and how often you're likely to use them when choosing your frequent flier program.
Does your airline of choice have a hub near your hometown or in the cities that you frequently fly to? Choosing an airline with a convenient hub will ensure that you're able to fly on frequent flier club's airline often, and usually for competitive prices.