Hi - sorry to see you have been ignored for two days!
I was a TA (male) in an infant school for ten years, and two years in a tough comprehensive. Began as a parent helper when our DS started in Reception; enjoyed it more than the office work I had done previously, and in due course got employment at a different school.
Presumably you will be aware how difficult a teacher's job can be, so anything that can make her/his day run a little more smoothly would be useful. Although teachers do SEEM to have eyes in the back of their head, and bionic ears that pick every little remark and murmur, they gain those skills over years of hard concentration, and are in fact physically, just ordinary people!
So, if you notice a child misbehaving, cheating on its work, looking near to tears, or (worse) looking like they might be sick or desperately need the toilet, then feel free to intervene, but in as unobtrusive way as possible, and - hopefully - without disrupting the lesson. Quite a tall order, I agree.
Teachers are not perfect, and can sometimes make mistakes. When I was first a parent helper, supporting reading in a Yr1 class, I must have come out with some nugget of information that surprised the child, prompting her to ask: "Sir, do you know EVERYTHING?" I explained that no one could know everything. Quite early on in my employed TA career, I was in a Yr1 one lesson, the children thinking of words beginning with the letter 'v'. A boy came up with 'vacuum cleaner', which was pretty good for Yr1 I thought. Unfortunately, the teacher wrote up on the board 'vacume cleaner'. Had I not quietly suggested that I thought it should be 'vacuum', then the incorrect version would have been copied down into thirty exercise books. (She also didn't know what a 'sloth' is, and really shouldn't have been in teaching, but amazingly, twenty years later, she is still there!)
I would certainly hope that your teacher will brief you as to the daily routine, what she would like you to do, who is on playground duty, where the coffee is kept, where the toilets are, etc. However, if she is NQT and this is her first 'proper' job, then it is just possible she might overlook some of these - rather important - details! In which case you will have to take the initiative and ask; again, unobtrusively. Another little girl I worked with in my parent helper days, turned up again in another school, seventeen years later, on her final year of Teacher Training! Now our roles were reversed, and SHE had to tell ME what she wanted me to do, and monitor my performance as her helper. (She qualified, and became a successful teacher.)
If you have any special skills, interests or hobbies, that might be relevant in the school environment - music, art, crafts, sports, etc - when you have settled in, see if you can support some activity or club. I taught informal recorder lessons for ten years, ran computer clubs, taught touch typing, had a percussion club for a while, and coached children to play percussion for the Christmas performance. After Yr2 SATs one year the teachers let the children relax, by working with me in small groups for three or four weeks, building a two metre high tyrannosaurus rex from cardboard boxes. As work progressed they took the various components round the other classes, explaining what we were doing.
By now I'm sure you will have realised, if you didn't know before, that helping in school can be one of the most important, satisfying and enjoyable things you can do. I wish you Good Luck, and enjoy it!