When you're in the wilderness, you need clean water to drink -- but water sources in the wilderness can carry bacteria such as giardia. You don't want giardia, trust me, and trying to carry a few jugs of Poland Spring would be extremely heavy and inefficient. Luckily, there are a number of ways to purify water, and one of the simplest, cheapest, and most effective ways is to use iodine tincture.
--Water bottle: A Nalgene (what I use here) or a metal water bottle will work best, but all you really need is any container that will hold water.
--Iodine Tincture Solution: You want Iodine Tincture with 2% Iodine and about 47% alcohol. Bottles of this solution should be available at your local drugstore and a 2 oz. bottle is usually $3 or less.
--An eyedropper: Counting the number of drops is the easiest way to keep track of how much you're using.
--A good water source: This can be a lake, a river, a stream, etc. If you have a choice of water sources, consider these two tips:
Clear water is better than cloudy water. Flowing water is better than still water.
Remember, though, that even if the water looks extremely pure and clean, it should still be purified before drinking. Looks can be deceiving!