I end up having between 2-4L most days, sometimes more, sometimes less...
If exercising I will up my fluid intake a lot to compensate for fluid loss, and if I'm partying I try very hard to drink a cup (250ml) of water an hour minimum, depending on what sort of partying
Incidentally, the new 'here is the amount' for recommended daily intake is 30ml per kilogram of body weight... for example 70kg person would then be recommended 2.1L fluid, and then advised to add extra for fluid loss from exercise or what not.
We get fluid from sources other than just water though, and even tea and coffee provide us with some of our daily fluid needs, despite the caffein & diuretic effects...
I definitely feel better, more alert and have nicer skin when I am being a good water drinker, and I find good hydration helps more to combat fatigue than a cup of coffee usually...
My biggest 'drink more water easily' tip is to keep a bottle in the car, and make it one of the ones with a pop top so that you can just grab it and drink, without buggerising around with screw tops, which ends up hindering your water-sippage...
As Henry Rollins said, "Be drinkable!!!"
:D