This is how I taught Shiloh, Delilah, and Chance shake. Chance learned it in only 1 day! o.O
First, your dog must understand the clicker or
a marker word. I like to say "yes." Chance learned this with a marker word, but I'm going to use the word "click" so I don't confuse anyone.
I simply lift the dog's paw, and click as I raise it.. Repeat that about 5-8 times during each training session.
Once he got the hang of it, I then try to get him to give me his paw on his own. I just pokec his paw until he give it to me. If he didn't, I'd go back a step and keep on lifting his paw.
Once he gave me his paw on his own reliably, I then added the cue "shake."
I hope this helps!