When I was training Lily to shake (give paw) I dangled a treat in front of her nose, kind of up high above her head, making her lift her front paws up. Once she did, I would grab her paw and shake, saying the command at the same time. Then I would give her the treat. It took her 2 weeks to figure it out, but she does it all the time now. She even has a new trick, we say "stick em up!" and she lifts both front paws in the air