I don't believe in water waste. I also don't believe in showering too often because it's not good for your skin. And since California is in a severe drought, I shower every other day. If I'm sweating and doing physical activities; I'll break the rule and take a quick 3-5-minute shower the day after I took one.
Once a day generally. Occansionally twice if I shower in the morning and then go to the gym later or go out to a club later, but I generally try and time them so I only need one a day (e.g. forgo the morning one for a later one)
Once. I can't do a single thing before I shower, so I do as soon as I wake up. I absolutely hate summer. It gets so humid here, I shower twice most days in the summer.