I have no idea how much water I need to drink. I'm not thirsty, and my mouth is always 'wet', even when I'm dehydrated.
My urine colour, however, is a very good indicator for me about how much water I need to drink -- too dark, drink more, too light (clear, even in the bowl) I'm probably drinking too much.
I just try to drink 'regularly' without any kind of schedule, so far so good.
Also, probably drink a little extra before bed -- I find myself waking up dehydrated most mornings, even after drinking a glass before sleep.