Play with words. Speaking is infinitely more appealing when it's made into a game. Then every once in a while sneak in a new word. If he doesn't know, whisper the answer and let him shout it out. Then, tell him what the object is and how it functions.
Most kids develop a fascination with the phone long before they can talk.
Use that allure to get yours chatting. When friends and family call to say hello, let your toddler tie up the line for a short time. With no visual cues to help, your child will be forced to hone his pronunciations. When he starts to get frustrated, however, it's a good idea to step in and translate . Ask the caller to challenge him with simple questions.