One thing I've read and tried to remember was that you should drink at least 64 oz plus 8-10 oz for every 25 lbs you are trying to lose. So I have been shooting for 130 oz of water a day. It sounds like a lot but that works out to about 5 bottles for me, and I can easily drink 3 or 4 just during work. I also tend to use my pee as a guide (see this
Perfect timing for that link Defining
! I'd be tempted to try to see how much water I lost during a workout, but they say try not to drink during and I'm fairly certain I would die attempting that lol!!