I have a 1.5L bottle on my desk at work. I normally get thru at least one and a half, sometimes two bottles over the working day (and that's not including what I drink at the gym in the morning, or at home at night!). I see it all the time so I'm constantly reminded to drink.
On the weekend it's a bit harder and there's a lot of guesswork involved! I need to work on starting to drink water earlier in the day on the weekends... normally it's a few hours before I'm off the tea/coffee and onto the water
And I never, never go out anywhere without taking water with me... just can't do it!