I have had braces when I was 12 and again at 29 (not orthadontist's fault but crazy subsequent dentist who removed all four back teeth in front of widsom teeth coming up, claiming the space would be enough room and my other teeth would definitely not be pushed forwards, grrrrr!)
I would certainly keep banging on about cleaning. I was lazy at 12 and ended up with a darkish mark around one of the brackets which looked like I had food on it for years until I got them bleached a couple of years back. I do wonder if this wasn't helped by the fact that I kept choosing alternate purple and green pads as colour choices, so if they can't have them you will probably be better off! Also with bleaching the white adhesive will always look whiter than the normal tooth so make sure they get it off as much as possible on removal.
Wires at the very back can be trimmed, I used to get problems with it sticking into my tongue even if just a mm out. I was given wax to put on any areas that rubbed as it takes a while for the soft internal parts of the lips to get used to it at first.
It will hurt and be hard to sleep, so anything caploleque you can give to help with pain will be gratefully received when they have just been tightened.
It will feel very odd for about a week after putting on and again when they are off, you mouth feels tiny and then huge again!
I do now have lovely teeth, and they will be happy with the results. After the first few visits they will know what to expect and it will hardly bother them 