This topic comes up a lot, I figured I'd post my method of removing and replacing these chips. I try to minimize the amount of time I have heat on the circuit board as lifting traces is frequently the death of the board. Some methods, such as a solder sucker and/or solder braid use too much heat for too long or subject the board to unusual stress, both things that I'd like to avoid.
With that in mind, I start by simply clipping the individual leads of the IC right at the body, one at a time. Then I can remove the body and leave the individual leads. It's very easy at that point to simply sweep them off with the iron.
After removing the residue of the old chip, it's easy to position the new chip on the pads. I tack one corner first and carefully align the chip with the pads. Then I tack the opposite corner to keep it in place. Finally, I solder the the remain leads once the chip is aligned and tacked in place. Of course, I also clean off the flux as the last step.