Quentin Quiet never says a word. You know he's done his homework, but he's just not comfortable talking in front of the group. You don't want to ignore him, but you also don't want to push him. What can you do?
Spend some time with him outside of the group. Make a point of talking with Quentin before or after the group time. Chat with him during refreshments. Meet for lunch if you can. Let him see you as a friend. If you have a co-leader, encourage him or her to do the same. Then bring another person or two into that circle, perhaps during refreshments. Before long, Quentin may forget how shy he is and be comfortable enough to risk an answer.
Call on him. If Quentin was raised under the philosophy, "Children should be seen and not heard," maybe he's just waiting for you to give him "permission" to talk. Some people feel that what they have to say isn't very important, but if you ask their opinion, they'll give it.
Find a question you know he can answer or one that simply asks his opinion. Smile and say, "Quentin, what do you think about … ?" Give him time to formulate his answer. Affirm even the shortest and most hesitant response. But also give him the freedom to pass if he wishes.
Go around the circle. Find a question you'd like to concentrate on and go around the circle. Say, "I think this is an important question. Let's have everyone respond in just one or two sentences." Start at a point where Quentin won't be first or last, but a little past midway. You've reinforced that you want short answers so he doesn't have to give an oration. Affirm each response to build his self-confidence. You won't want to use this often, but once in awhile it may work to break down his barriers. Again, if he passes, simply smile ...