I typically count Class Participation as 10% of the course grade, so this tends to encourage participation. Also, I let students know that if no one responds to a question, then I may cold call. If I have to cold call, I try to select students who I think are likely to get it correct (I am not trying to embarrass anyone). I also reach out to students (outside of class) who are not actively participating to encourage them to speak, even if it is just to ask a question.