Students sign up for class and volunteers from the community come to meet the folks from other countries. It's quite mult-national. Students and volunteers sit at tables and are given questions by the instructor to guide conversation.
People can talk about anything they want, but the questions are there in case the conversation lags.
It depends on the student to volunteer ratio. After about 20 minutes partners can be switched and the volunteer has the opportunity to meet several students. We also have a class called Bilinual Conversation, which is only for ESL and Spanish students. Learners of each language meet and are given a topic and vocabulary for that topic. We do an hour in Spanish and an hour in English.