I do not believe in 'rules' in the sense that we are all different and have different lifestyles and needs.
I drink a glass of water and 1of juice at breakfast + 1/2 pot of coffee.
Before bed I drink at least 2.
During the daytime I try to drink whenever I am thirsty (water only) and at meals a drink at least 1 glass.
I figure that gives me what I need. At work, I try to keep refilling my water bottle and that tells me +/- how much I am drinking.
I drink more in the summer or if I am active. I drink more if I am stressed or my output is too thick. I drink more if I feel light headed.
Most often I drink water but I make a jug of lemonade ever day. Fresh lemon juice (or concentrate), mint leaves, fake or real sugar.
My rules a simple really, try to avoid mineral water and drink mostly filtered water whenever possible (my nephrologist advise me of that after I had my 1st kidney stone), avoid pop, sugary drinks and too much juice (mornings only or very diluted), coffee is my drug. I drink 5-15 daily depending on if I am working or not...my body likes it, yours may not. I do herb teas at night, whatever I have in the house.
I avoid milk because my pouch hates lactose (I get enough with ice cream and yoghurt).
Your body will be able to tell you what it needs if you know how to listen.
If you are getting headachy, weak in the knees, seeing stars, dry mouth, papery skin then you should try upping your intake. If your urine is too dark or smells strongly then ditto...increase water.
Other than that follow you gut...pun intended!
Sharon