If everyone is too quiet, make a game out of it. Pass the microphone around and ask a question such as "What is the first word that comes to mind when I say... Porcupine?". Then, everyone in the group individually says the first thing that came to their mind into the mic and passes it to the next person. The person responsible for asking the question rotates to the next person on their right. (or left. It's your house, your rules) At the very least, some of the answers will be humorous.
This idea works great for teens. Of course, they will be quiet at first. But leave the room, let them put on their own music, and wait for the magic.