I keep a pitcher of water in the refrigerator, which stores my 8-a-day. It's easier to track because I can visually see how much more water I have left. Plus, I have a horrible memory so sometimes I forget which glass I am on.
I got a new pitcher for Christmas that has an insert in the middle that I put sliced lemons, limes or oranges into- depending on what I have on hand. (I don't like plain water as much.)
When I was working, I would fill up a thermos to use while I was away to keep track.