You would come to the phenomenology seminars.
In terms of teaching, I'll likely ask you to help teach some examples classes on my part III course: Symmetries, Fields and Particles. It's good cash and looks great on a CV. You would mark test, set by me. You would earn decent cash doing this. This is the "Early Offers" test: probably less than a day's full-time work. There will be model solutions and a detailed mark scheme, and I would go through how to mark (etc) with you. I'd also check a portion of your marking (particularly the first few scripts), and look at any queries you have.
Your first research project would be set by me, and we will work on it together. After this, I'll encourage you to also work with others (perhaps with me as well - perhaps not) in Cambridge - this is very handy for getting other referees for future job applications (typically, you need three).