Ask for help when you need it. If you're struggling with a class, ask the professor or your advisor where you can find help. If you're struggling with life, find a counsellor. If you're struggling with a paper, find a writing tutor.

Take introductory Calculus, Chemistry and Physics in your first year*. At least at my school it was somewhat difficult to complete a science major in three years, so best to start off as though you are going to do one (unless you really don't want to).

Find a way to contact and talk to people who are where you want to be in the future. That might mean law students, engineers, med students, people working in finance.

*Unless you are doing Engineering in which case your schedule is mostly decided for you.