It is a common misconception that animals are best stalked from above. Perhaps this is because hunting from a treestand is so effective. But ground sneaking and tree sitting are worlds apart.
In my experience, stalking down from above a deer, elk, or bear is the worst possible choice. Critters in the hills tend to keep a wary eye above for predators, and a bowhunter is most likely to be skylined and easily seen during a downhill sneak. Raising your bow to shoot downhill can present a stark silhouette that scares the heck out of animals.
It is almost always easier to hide if you sneak along a sidehill or approach from below an animal. A sidehill stalk allows maximum use of ridges and ravines that naturally run down a slope. Getting below game prevents you from being skylined and usually provides ample foliage for effective sneaking.
When given a choice, I never stalk big game from above. Sidehill stalks are my favorite, because the undulating, water-worn nature of most slopes gives me solid rock and dirt to hide behind. If I am able to come from below, I know I'll always have a solid background that eliminates my silhouette and enhances the value of my camouflage clothes. By comparison, sneaking above game is usually a disadvantage.