It probably depends how old your students are, but with my adult students the two biggest wins are: 1) Romance. Dating and marriage, etc. 2) Themselves. Folks love to talk about themselves. Of course, those two topics only seem to go so far, and even then there are some students who just wont respond. I have to do an English Corner every day at my current job, and I often end up ripping my hair out thinking of topics that will get them going.