I want to stay hydrated, but don't want to have to stop to use the restroom more often than necessary. How much water should I be drinking, and when?

I know this sounds simplistic, but it works for me, and I believe it.

A coach I had in high school told me that my body knows how much to drink, and that drinking when you get thirsty is the best method. I have friends who drink in anticipation of the thirst, and I've seen no ill effects from that method, but I am a firm believe that the good Lord made our instincts and inborn urges for a reason.