What works for me is to get my riding clothes on, put on sunscreen, go to the bathroom, then just before I walk out the door I will drink about 150-200 mL of cold water and fill both of my 25 oz (.75L) bottles with a few ice cubes and cold water. I take a sip (~50-75mL) about every 15 minutes after the first 30 minutes or so. This amount of water can carry me for about 4 hours before I need to refill. So about 375 mL per hour of water intake. I don't bother with gatorade, salt, or food unless I'm going to be out more than 4 hours.