There are three basic types of marking situations when marks of the gun can be utilized:
Dogs positioned by the shooter's side (waterfowl/dove)
Walkup or driven shooting, the dog at heel (upland game)
Flushing (quartering for upland game)
In each of these shooting situations, the young dog can effectively learn to mark game fall by noting the direction of the gun barrel and shot. The barrel guides the eyes and pinpoints the target for the retrieve.
The first step is to get the young dog to watch across fields or water for potential marks. The handler stops throwing bumpers as quickly as possible in training - instead use a remote launcher or assistant to attract the attention of the pup. As the thrower appears, the handler whispers, "Watch." Soon, the pup will begin to scan the horizon in anticipation for the "watch" cue. The mark is thrown along with an audible sound from the thrower.
Next, hide the thrower. Use the "watch" cue prior to the flyer's appearance. Accompany the mark with an audible sound from the thrower such as a shot popper, duck call or verbal sound. Begin pointing out the area the flyer will originate at the time of the sound with a long stick, cane, toy gun or a long makeshift gun made by taping a broomstick onto an old rifle stock. These become your pointers. Swing the "gun" as the mark arches high across the sky, and trace it to the ground. Hold the gun on the mark briefly, allowing the image to be established for the pup.