Here's how to teach your dog to give you a high five.
High five is simply slight variation of shake. So you'll need to teach him to shake before you can teach him how to high five.
Ask your dog to shake but move your hand towards him with your palm facing sideways. Take his paw like you do when you usually shake, click and treat. Repeat this a few times to get him use to your hand approaching his paw in a different position.
Now ask him to shake by approaching his paw with your hand as normal, but as he presents his paw twist your hand so your fingers are facing up, and gently push on the bottom of his paw with your hand, like you're giving him a high five. Click when your palm makes contact with the bottom of his paw and treat. Practice this until he is high-fiving every time for a click and treat.
Now introduce the cue. Say, "high five," and click and treat every time he gives you a high five after you've given the cue.
Next: Roll Over