First, accept your teen as he is. Don't push him beyond his abilities to cope at the moment. Help your teen take little steps toward conquering his shyness, to the extent that he can function in ways that he wants. The discomfort of shyness can fade with loving support and encouragement. Second, if your teen lacks social skills, help him to learn.
Role play beginning conversations or asking questions.
Practice builds confidence. Third, take care with your criticism. Let your teen know that he is loved and that your don't expect perfection. The Parenting Resource Center on the Web.