One of the most important things about any physical activity is staying hydrated throughout. When going on a backpacking trip usually you are having days of prolonged physical activity so staying hydrated is even more important.
With no physical activity, on a normal day men should be drinking approximately 13 cups of water and women should be drinking approximately 9 cups. When you are being active all day long that number goes up. I would recommend drinking at least one cup of water every hour.
You might think that this is an unrealistic goal, but it really isn’t. One cup is 8 ounces and the normal nalgene water bottle has over 32 ounces. So you need to drink one entire water bottle every 4 hours to stay well hydrated.
Depending how much you sweat will also change the amount of water that you need. Those of you that sweat a lot might need double the intake of water.
When I am backpacking I find it a hassle to have to stop and get my water bottle out of my pack every time I need a drink. I prefer to use a hydration pack that has a hose and spout right at my mouth so that I can keep taking sips as I go.
A lot of backpacking packs have sleeves built into them for a hydration pack, as well as a port for the hose to come out of the pack. If your pack doesn’t have either of these you can still travel with a hydration pack, you just have the hose coming out where the zippers meet and secure the hydration pack upright where it won’t get too squished.
Be sure that the water you are drinking is clean water by using a water filter or purification device.