Everyone develops their own style as they gather experience, based on what they discover works best for them. My GoLite Quest pack came with a pocket for a hydration bladder, but I always use a 2-liter Platypus and just lay it horizontally at top of my pack. This makes it easy to access.

Eventually I just cut out the bladder pocket from that pack, as an unused feature and therefore useless weight (it weighed maybe all of 20 grams at most - grin ).