You can certainly take a lot of actions to explore the various domains you could focus on in school. However, you also don't really need to be too concerned about it just yet. Look at the coursework, try out some new things, talk to other students and professors. Explore as much as you can your first semester, and let that help guide you. Sometimes you have no idea what speaks to you under you're stuck in a class doing it. Likewise, you might realize you don't actually like doing what you dreamed of doing. Try on as many hats as you can.