Items inside stashes can be a wide variety of items, medical equipment, ammunition, armors, weaponry and artifacts, although all stashes have specific contents and are never randomized. Most of the time you will have to get stash locations by searching dead bodies of stalkers (including zombified stalkers) and they will give a random stash coordinate. Them giving the coordinates and chances of them giving it are completely random, once you obtain coordinates of a stash it will be displayed on your PDA as a violet circle with 3 triangles inside, you will also be prompted with a ping. However, in Clear Sky and Call of Pripyat, ammunition containers near outposts throughout the Zone and in faction bases might contain some supplies that can be used by the player.