Purchase your flight using an airline-affiliated credit card. Many airlines have deals with credit card issuers. For example, Delta has a SkyMiles affiliation with American Express. If you use that Amex card to purchase your Delta flight, you may be able to get one or more checked baggage fees waived.
Join an airline's frequent flyer club. All airlines have some kind of frequent flyer program where you get perks the more you fly. One of those perks on some of the airlines is a waiver of the checked baggage fees. How many miles need to be earned to obtain this benefit will vary. If your airline of choice does not offer this as a perk, it never hurts to ask. Flaunting your frequent flyer status may get an attendant to waive the fee in order to keep a repeat customer happy.
Alert the ticketing agent at the check-in desk if you have an international leg on your flight. Many airlines give waivers or discounts on the checked baggage fee if you are traveling internationally. This includes some domestic and nearly all international carriers. Even if you switch to another airline, they may waive the fee as long as the flights connect.
Upgrade the class of your ticket. Some airlines charge the checked bag fee for economy class, but may waive fees if you upgrade your ticket to business or first class. Of course, this will cost more than the checked baggage fees themselves, but if you have airline miles or frequent flier points, the upgrade may be free.
Show your active duty military card. Active military members and dependents can get the checked baggage fee waived on most domestic airlines.
Ask. This may sound simple, but if you ask and have a valid reason the fee should be waived, the airline employee just might do it. For example, if your plane was delayed or overbooked, complaining about it and asking for the fee to be waived may work. It never hurts to ask.
