The idea is to teach him the word no, so consistantly use it for the same thing and when he gets it go over the top with praise ie, yeah well done Jer ! What a boy ! Wow ......

Try to use it as often as you can remember it really is just like training a puppy lol. And pups get the word no real fast.

You cant stop and start, its a forever thing so they get the message...

CONSISTANCY