Focus on getting to know your professors, explore your options by taking part in research and internships.
And I second this advice, regardless of where you go. So many people enter undergrad thinking only about what to study and downplay the crucial role of developing and maintaining good relationships with professors. Not only is this an end in itself, it is also very important when the time comes to ask for recommendations for grad school or work. When you get there you do not want to be in the position of a beggar, asking uncomfortably if a professor whose class you got an A in but haven't talked to much will write you a good reco. What you want is to develop good personal relationships with them so that they *want* to write glowing LORs for you.