Moving onto supply you start to realise just how much of your behaviour management comes from your established status within a school. You need to find a system that works in short bursts, when you may never see that class again after that lesson, and when the class know you've got minimal authority with regard to sanctions (because there are schools that will overrule anything you try to do on supply - and boy oh boy do the kids know it). You can defuse a lot with your own teaching presence - but you come up against classes that are determined to crack a supply they see as fair sport, you come up against teachers who set classes up for you to fail ("I know Mister X isn't me and you find it really hard to behave for supply teachers but I want you all to try really hard and we'll go over anythign you haven't done - translation: don't bother doing it I don't expect you to - next lesson") and you come up against not knowing routines/timings/changes and one-off assemblies (how I love you the second Monday in March everyone knows it's Esperanto Assembly oh didn no one tell you). Learn a few names as quickly as you can (the trouble makers normally identify themselves to you within about 10 seconds of the beginning of the lesson), do the best you can - but it's a different kettle of fish to full-timing and something you get better with with practice. Basically it's the same stuff as your first day on teaching practice - FEEL like you're the boss, ACT like you're the boss, act like it's your room for the day and take it from there - there's advice like controling entrance to the classroom, making sure stuff's to hand (which can be harder on supply) and the like - but that's down to your own teaching style really.