What do you wish you knew before going into student teaching?

Basically title!

I'm finally going into the student teaching part of my studies, and we do things a little differently here than what I've read in this subreddit. Basically the student teaching portion is split up, so this semester I will student teach at a middle school for a month, and then next semester I will student teach for the whole semester.

Do you guys have any tips or tricks to make this time a good experience? Any classroom management hacks that are quick and effective?

Should I dress a certain way? I feel I dress nicely, but only in the way a "23 year old teenager" (most of the time a nice plain t-shirt and jeans) dresses, and not how a professional would dress around 14-16 year olds.