As E Cameron said, the 6-8 glasses a day thing is a myth. It was started by an early 20th century health guru (hard to explain, but in the early 1900s in the US there were a lot of quasi-cults built around 'heath gurus') who came up with the number with pure guesswork and assumptions. There is no scientific basis for it and no one has bothered to do any research on the topic until very recently.
Recently established after the first attempt to actually come to a scientific conclusion and with the intent of actually supporting the myth, it was found that under normal conditions (not sweltering heat, dry conditions, or stenuous exercise, etc), and with a normal diet, your average human does not need to drink. We get ample water in our food to sustain our daily water loss and function normally. The food we eat has a very high water content. Some foods like greens are almost entirely water.
As was also said, if you're in need of extra water your body will tell you. You'll get thirsty, your lips will dry out, etc. Of course it doesn't hurt to drink more (up to a point) if you feel like it. You'll just do more urinating. It can provide some benefits, though, in instances such as trying to flush out a virus or flushing your UTI to help clear an infection.
I usually drink 30-40oz in a day. I get a lot of exercise running all over the place and I use soda to stave off hunger. I also quite enjoy the taste of tea and hot chocolate. I also drink fruit juice to help get in my fruit related nutrients.
