Dos which might seem obvious, but clearly aren't to everyone are: Do arrive on time and make sure you stay for the whole school day including any departmental meetings (citing problems with childcare is not good enough).
Do make sure you know what a scheme of work is and how to use one.
Do refrain from sneering at the teaching staff and the children and remember to be polite in what you write in your notes too. Your mentors and the head will see them, as well as your tutors back at university. Dishing it to the school or a particular teacher is not a good idea.
Do know what you're talking about: it's not a capital offence to admit ignorance (though obviously it's better if you don't have to), but giving out wrong information is a no-no.