Hi Katelyn! It is so exciting to hear about other upcoming teachers! When it comes to student teaching, I think the biggest things are not being afraid to ask questions or concerns when it comes to becoming a teacher, knowing that you are also (somewhat) in control, be open to more effective teaching strategies, and that (hopefully) your assigned teacher is there to help you. I know that when I was a sophomore in college at my first placement, I did not know a lot of the 'behind the scenes' stuff when it came to teaching. I did not know about the IAT process, IEP meetings, effective planning, etc. I felt like I was going in blind to my proper student teaching experience.
The 'control' thing can be hard, because it depends on the dynamic of the class. However, letting students know that you are also in charge helps you feel like a teacher and the students SEE you as one. It may feel like you're stepping out of place and/or being a little mean, but if your assigned teacher is good they'll respect it. That being said, TAKE ALL THE CONSTRUCTIVE CRITICISM AND ANALYZE IT. Take advice and see if it fits you. If not, know that you don't have to use it, but you should 'keep it on the shelf.'
Sorry this was long, but it is something I wish people would have told me. So good luck! Be confident and change the world!