How much water should we drink??

I don't know about the rest of you- but one thing that I sometimes struggle with is drinking enough water! Some day's I am great at it and feel like I might slash-swash while I walk, other day's I feel sooo thirsty by night time or when I wake up in the mornings.. So here is what I found out about drinking enough water each day...

You take the # of lbs that you weigh and multiple it by 2/3's   = the number of ounces per day you should drink!
ex: 150lbs X 2/3 = 100oz of water!
I found an awesome article