Have a plan (or several) for what you want to do with your life. The AAAS (American Association for the Advancement of Science) has a website tool that is supposed to help you identify possible career choices. But your idea may not be on there.
Find people who have realized the life/career that you want to pursue. Ask them for advice on how to get there. You must do this! It will be near impossible to figure out what you need to do, how you need to prepare, what you need on your CV otherwise.
My career is in academia, so almost everything that follows is specific advice about how to become a university or college professor, although much applies to any research-in-science job. You should however find out advice from others, and get inspired by great models - e.g. listen to podcast interviews of scientists.
If you are thinking about a career in research:
Most importantly you need to become member of a lab and do research. I see these as two distinct things:
Develop connections. Scientific networking in your case primarily means developing a connection to about 2-3 professors who will later write recommendation letters for you, your research mentor being one of them. In addition, learn the research question and approach of every other student (grad or undergrad) in your lab, and make sure they learn yours.
Do research. All successful scientific research ultimately is published as a 'scientific paper', and thus your aim should be to be involved in one (or more, if you start early). My advice on how to do research.
Plan to apply to graduate school: here is advice on applying and interviewing. Know that in grad school, unlike college, you usually get a salary and your tuition is covered. You should ask details about how this works when you are interviewing for a program, but there is also often information on the program website. You must start this process early (see the advice on applying); plan to write inquiry emails to prospective advisors in the summer a year before the fall in which you want to start grad school. It will also take you a while to select the programs to apply for - seek advice and suggestions on this from your advisor and from every grad student, postdoc, and senior undergrad you can find (especially your lab mates). Finally, look around. There are many other websites that give advice on how to get into and do well in grad school: e.g. Matt Might.
On that note, I also recommend reading a bit about what grad school is like, so you are not naive in deciding to do it and when interviewing for it.
Also, apply for the NSF GRFP. These are grants from NSF to pay you in grad school, something you don't need to live (see above), but they will make your life a lot easier (because you will have to teach less), AND they will make getting accepted into a good program easier. Assume you will write one in your senior year, and another one (or more) once you've already started grad school. Talk to your prospective advisor (!!) in detail about this as soon as you are admitted anywhere.