Watch for airline promotions, especially new service routes and online booking bonuses. But don't spend money just to accrue miles. A frequent-flier mile is worth only about 2 cents. Forty percent of air miles are earned on the ground. Credit card companies are the primary source.
Most cards offer one mile per dollar spent.
American Express has the best affinity programs, but its fees are the highest. Telephone deals rate a close second for ground bonuses. Many long-distance carriers offer bonus miles for switching to their company. Research carefully before agreeing to any long-term commitment, or risk forfeiting miles earned. Web sites such as ClickRewards present opportunities to earn miles by shopping at selected online locations.