It just takes doing the same thing over and over until the "light" goes on for a puppy.
With my girls, I first asked them to "stand" for their treat… if they jumped up, the stand command was repeated... the second they stood, they got the treat. And believe me, you had to be quick with two wild things... They figured it out pretty quickly... then I would add the "stay", so it then became Stand/Stay... again if they stood, they got the treat. Then I added a step back with the Stand/Stay, again the second they stayed, treat time.... and so on and so one. Worked for them really well....
As far as "stay" for their regular food, I feed them in their crates which are in a different room then the kitchen. When it is time to eat, I just tell them "Kennel" and off they go....