Jackson is a very smart dog, but "Shake" took him FOREVER. For a few weeks, I would randomly just pick up his paw, shake it, and say "Shake" and give him a treat. He just never would do it on his own. I even tried using the word "Paw" thinking maybe it was the word. Then one day, after 2 weeks or so, I asked him to shake and he did it! LOL. I don't know why that trick was so hard for me, but just keep working on it
He now knows like 13 tricks or so.