I first got involved with the SU as an Academic Rep - there was an issue on my course where students had to buy their own materials, which could get quite pricey. The SU trained me and gave me support to win a change on my course (we were given some free materials!).
My top tip for this year is to get involved with your Academic Society, and if your course doesn't have one then find two other people and start one. They're a great way to meet your course mates, share important information and gain new experiences through guest lectures and workshops.