Here are two handy tips that will save you money the next time you travel:
1. Don't buy water - If you have flown in the past 5 or so years, you'll know all about the ridiculous liquid ban on flights. So instead of buying a bottle of water for $5 that would normally cost $0.50, bring an empty bottle (either the ones that are en vogue now, or just an empty plastic one) in your bag through security. They'll know if there is liquid in it or not. Then go find one of the water coolers, or go to a fast food joint in the airport that has a self-serve soda fountain and I guarantee you there will be water there. And you can even get ice while you are at it. I've not been stopped once for doing it although it's not like I'm making a spectacle of myself about it either.
2. Don't pay to check your bag - This only works if you have one reasonably sized bag to check. The trick is to act like you are going to carry it on. Of course that means that you have no liquids larger than 3oz, or whatever the dumb rule is. But bring the bag with you through security and when you board just have the gate agent check it. I guarantee you that they'll do it since they will no doubt run out of overhead bin space when all is said and done. The gate agent will gladly check your bag to your final destination and you didn't have to spend the $25 to check it. This is especially convenient if you have a connecting flight and don't want to be dragging your bag with you through a gigantic airport like Dallas, Chicago, Denver, or Atlanta.