I haven’t linked to the Cult of Pedagogy in a while, but this site is actually the first I check when I want to find reasonable, practical and up-to-date advice about teaching. For example, this post about dealing with excessive talking in the classroom is an absolute must-read. And the key idea is just that: prevent misbehaviour rather than scold them afterwards. First you define expectations, then you model and practise – like a real lesson – and you hold them accountable. You can’t really expect them to behave unless you’ve specifically taught (not just told) them how to! Very obvious, but so very true.