1. The classes that you'll take: In business, there are Intro to Higher Education (IHE) classes and lower division classes that will get you a better idea on the topics of business you may like: Accounting, Finance, Computer Information Systems, and so on. If there's a class that you like that may influence your decision on that branch, then try it out.
2. Clubs and organizations: You should participate (or be in the leadership) of various business organizations. They will bring speakers from various industries and departments that may influence on which branch you want to be part of. That's how I knew what Big 4 accounting firms are.
3. Extracurricular or Faculty Projects: If your college/university has availability to participate in presentations that are from your own faculty/professor or a competition from a club/outside organization, you should give it a shot. It will give you an idea on what skill you want to apply on, which may give you an idea on which branch you want to decide on.
Ailee recommends the following next steps:
What job do you want -> find an example job description -> what are the requirements for the job and what degree(s) does the job ask for -> is that degree(s) offered at your school -> are you interested in that degree
Hope this helps some!
I really enjoyed Economics but I'm also a math nerd, so I enjoyed Accounting and Finance as well. And the skills I developed in those classes helped me in my major as well. But remember, that your job is to stand out to an employer and/or grad school, if you take that path before starting your career.