Amongst the 4 common fees and how to avoid them, U.S. News & World Report suggests this advice about how to avoid paying fees for luggage on an airplane, with which we concur:
If you must fly on an airline that charges for bags, pack light. Check in with any rewards clubs or frequent flier rewards representatives to see if you qualify for discounted luggage fees or maybe even a waiver of the fee. You may also want to check in with the airline’s website to see if it’s cheaper to pay online for the baggage fee than it would be to pay at the airport. Another option for longer trips is mailing your items to your destination through the postal service. The cost for postage might be cheaper than the extra baggage fees.