Most of all, socialise. Find societies and events that interest you (curricular and extracurricular). Go to careers fairs and networking events - not necessarily looking for a job/internship right off the bat, but just getting a feel for what's out there.

Put the required effort into the course to pass it, but not much more. Except for the topics that genuinely interest you - go deeper on those than anyone expected. Prioritize your own understanding of a topic over external metrics.

Email or visit your lecturers to ask questions. Email the authors of papers you read.

Start building a portfolio and/or [micro]blog. Even a "hello world" github repo acts as a proof-of-humanity when you're applying for jobs in a few years time.