First of all, congratulations! I can't begin to describe what an amazing opportunity this is going to be for you. You should definitely be excited for what's about to come with your sessions and teaching! In a challenging class like AMS 11A, you'll find frantic students coming to you confused by the complicated theories described in class. Although this can be scary if you're a first-time teacher (like I was), you just have to remind them, and yourself, of what the basics are. How do you find a derivative, limit, one-sided limit, etc.? Even though every theory explained in class is extremely important, it's not what the students are tested on and expected to know in full detail. It's hard to be able to differentiate the different notations of expressions and understand the terminology! If you are terrified of public speaking like I was when I started this position, just remember to talk loudly and practice beforehand so you can just talk to the class instead of reading the paper (trust me, it helps)! Just make notes of everything you want to say and you'll be golden! Also make sure you pay attention in the lectures throughout the quarter so you can differentiate what they need to know and what they won't be tested on. For each of my sessions, the goal I usually came prepared with was concepts they were going over for the entire week (usually 3-4 concepts). It was really helpful already having a plan because when you ask students what they want to go over, you won't always get a response! Once discussing a concept with the class and asking questions to see what they do know, I found it easiest to work out an example problem on the board, then have them practice on their own or with others and share on the board afterwards. That way, they learn each concept they need to know, and are able to practice on their own, which is the best way to practice math problems.
When doing examples, try to focus on application problems (from either the book or Katznelson's Review Questions online) because those are perfect practice for the midterm and final and what they ultimately need to take from the class in order to move on to AMS 11B.
If you have any other questions about anything that you encounter throughout your MSI experience, feel free to contact me via email!