As you said....there are a ton of different answers out there. I got this off of UPSers.com.
You should drink approx. 4 to 5 eight oz. glasses of water per shift.
My suggestion would depend on the heat and physical exertion you expend. This is what I try to do. ultimately you need to look at your own body type, the way in which you expend heat through perspiration and how much energy you expend during physical exertion.
Next time you visit a doctor ask this same question!
For myself I use this...
Rule of thumb --> Drink one 8 oz glass of water for every 30-45 minutes of work. You can adjust this based on the heat, exertion and your ability to adapt to those conditions.
Carry the water with you - do not rely on a drinking fountain. I was also told by a doctor that water was the best hydrator. (sooo that means less "Gatorade" type drinks and more water)
Another thing - the colder the water, the more energy is needed to expend it. I was told by a doctor that drinking cold water during a meal inhibits proper digestion. Room temp is better!