Don't forget about your airlines' limit of # bags: some are now charging for each checked bag, but with a limit of 2.
Don't show up with 4 small bags that may weigh a combined weight of less than 50 lbs. Any excess #bags beyond your #allowance will be charged.
Currently, some airlines are charging $25 for the second bag but the 3rd @ a very stiff rate! Pay attention to the airlines rules closely or it will cost you dearly!