Increase time gradually, in small incriments, but also keep the intervals random. Dogs are very good at picking up on patterns in training, and if you always have him stay for the same amount of time, he'll learn that the command means stay for just that amount of time. So mix it up so it's less predictable.... 3 seconds, 8 seconds, 1 second, 12 seconds, 5 seconds, etc...
Another thing that helps is to give the pup little food rewards while he's holding the stay. Have some good treats, and treat him in the stay position, telling him "good stay". Keep these somewhat random as well. Being rewarded while he's IN position, rather than the big reward only coming once he's allowed to break position, makes holding the position itself a good thing to the pup.
And remember that there are 3 major things that need to be overcome when it comes to teaching any sort of place command like a stay: length of time, distance from the handler, and distractions going on around. Only increase one at a time, never try 2 or more at once. So if you're working on increasing length of time, stay close and minimize distractions. When you want to work on being able to move farther away from him, keep the time a bit shorter and distractions to a minimum, etc...
Another thing that helps is to give the pup little food rewards while he's holding the stay. Have some good treats, and treat him in the stay position, telling him "good stay". Keep these somewhat random as well. Being rewarded while he's IN position, rather than the big reward only coming once he's allowed to break position, makes holding the position itself a good thing to the pup.
And remember that there are 3 major things that need to be overcome when it comes to teaching any sort of place command like a stay: length of time, distance from the handler, and distractions going on around. Only increase one at a time, never try 2 or more at once. So if you're working on increasing length of time, stay close and minimize distractions. When you want to work on being able to move farther away from him, keep the time a bit shorter and distractions to a minimum, etc...
