Everytime he does bark, say 'speak' (or the same in whatever language you wish!) And when he barks after you say speak reward him. You only reward him when he barks when you say speak, not for any other barking. He will soon learn to bark when you say the word. The other advantage of this is you can then teach him the 'quiet' command. ie:the opposite. He barks, you say quiet, if no bark then reward. They soon learn. I wish I'd bothered to follow through with this....