It is more satisfying if you can take a particular subject/area - you will then have to assist the teacher when assessing/reporting on it. If you have a particular strength, use it: if teachers tell you they want certain objectives addressed you can still take your own approach (music, art, drama, ICT etc). If you are presented with planning remember it is MUCH easier to follow your own planning and use your own resources than trying to follow someone else's - especially if they knew that they would not be the one teaching with them. I have been presented with resources marked Low/Middle/High and recorded as such but then discovered working groups called a variety of names, none of which appear on planning. I have also been given planning that didn't make sense or match the resources alluded to. You get PPA too and you should make use of it for this kind of preparation and marking. Don't let teachers be lazy - if they want something specific taught in a certain way, ensure the means are there to teach it, the objectives are clear, the school/class has the necessary resources, the classroom is properly equipped, routines / groupings are explained etc. A simple instruction like 'children to record on whiteboards' can take up 10 minutes of a lesson as you discover half the pens don't work, children endlessly negotiate who gives what out or they don't know where things are - later you discover it should have been paired writing or that a particular child should have had a particular task and they are now weeping in the corner.... TAs work with the class, not a teacher, when you are with a class, the TA should be there - not 'helping' the class teacher on PPA - unless you say so. Don't make changes to people's classrooms, make suggestions or requests - it's the professional way to do it.