To teach a dog to shake/paw (put their paw in your hand) I personally like to begin by rewarding the dog for pawing before they know the command. Many dogs actually already shake naturally as either a way of playing or trying to get attention. This tells the dog that it's a desirable action before giving a name to it.
What I like to do is teach the dog to shake as a way of asking to be pet. Warning, if your dog is particularly needy you may not want to tie shaking to being pet or the dog might start whacking your arm while you're relaxing.
If the dog isn't naturally paw-driven, what you can do is gently pick up one of their paws then reward them. With a little repetition your dog will learn that the action equals a reward too.
Link to a Youtube video tutorial training shake