Drink a lot. Think of water as the body's transportation system. It helps blood flow (blood is about 50% water) deliver energy and antibodies to fight infection as well as it helping you remove waste through sweat and urine.

But not too much. You should not drink more than you feel thirsty. Drinking more than what you loose through exercise can be dangerous.

And what water is best? Starbucks water. Seriously. Tap water is better for you then bottled water as there are many more controls on the quality of tap water then bottled water (which is often just bottled tap water, often from the other side of the planet).

Tap water might not taste good where you live though - it tastes like limestone where I live in West London UK - so here is a great tip: When you are at Starbucks, order your coffee and ask for some water. They will serve it to you for free from a very good water filter. Nice and cold. I suggest you use a small water bottle though, so you don't need to waste a plastic cup every time you get thirsty.