Keep the area under your seat clear
So, you thought you’d be clever and pack two weeks’ worth of clothes into your “carry-on” and stuff that oversized bad boy in the overhead bin. But wait, now your “personal item” is full of books, computer gear, and stolen copies of SkyMall, and it’s taking up all the room under your seat. Which means no room to exercise your feet. Shell out the $25, check a bag, and save yourself the blood clots. Or, bring fewer copies of The Da Vinci Code.
Rinse your legs in cold water
Obviously, don’t do this ON the plane or you’re going to end up on this list. But once you get to a place where you can rinse off in private, deluge your legs, ankles, and feet in cold water. This will force your veins to contract and thus reduce swelling, similar to a pitcher icing down his arm after a long game.