Zalo, congrats, I'm so excited for how amazing the next 4 years can be for you! I'm a 2011 grad (Carnegie Mellon for undergrad -- econ&math plus a couple minors, now at a Top 10 school for my PhD). So I hope I'm close enough to school/getting my first job/all that confusion to have something useful to share.
As a recent undergrad, my advice:
1) Definitely do a double major or add a bunch of minors. One of the majors or minors should be very technical (math, physics, computer science, electrical engineering). You should make sure to get all As in those classes -- they will be your signal that you are technical and can do quantitative work. Sending this signal will mean that a lot of companies in other fields will be interested in you, because you can be taught to do what they need.
2) With the double major, it helps to do something that is a bit easier and practical as one of them. I'd suggest econ or business. (Hopefully I don't offend anyone with that statement -- as someone who did econ, I personally think it's 'easy' as compared to math, physics, CS, electrical engineering, etc). Business especially will be much easier than technical classes if you are able to write well and work in a group setting, thereby giving you the opportunity to kick ass at all of the technical classes.
3) Your school will have a wealth of resources -- use them! Go to lots of lectures (to figure out what you're interested in), talk to your professors a ton (go to office hours -- great way to get the professor to know who you are, to later be able to write you letters of rec, suggest you for research or awards, etc). Try to get to know people from all areas of study -- intramural sports teams, clubs, dorm/housing connections, are great for that.
4) The most important thing for getting employment is having work/internship experience. Spend your summers doing something! If you can't find an internship, use it for something product like teaching yourself a programming language or taking the GREs (just in case). But definitely try to get an internship if you can. I find that academia can be very insular and unfortunately there's not enough focus on work experience (which is the #1 beneficial thing for getting a job).
From the perspective of being involved in hiring new folks during my brief stint of working:
Be a whole person, with interests. A 4.0 looks great, but a 4.0 without any work experience, club leadership, etc, can be a little concerning. You might still get an initial interview, since companies often use GPA thresholds for hiring, and think someone with a stellar GPA is worth looking at. But when you're interviewed, people are looking at whether they want to work with you, especially at a high-stakes, high-salary, time-intensive job. (Like consulting -- an old colleague used to always joke about the airport test, that you shouldn't hire someone who you would find unbearable if you were stuck at an airport with when your flight was delayed or cancelled.) Leadership positions are impressive, while activities, research, or grants give us an opportunity to discover what you totally geek out on.
And just in general, I hope you're able to enjoy life, as it is today. Planning for the future is awesome, necessary, and you've got a great head start due to think things through so early. But there's no point in putting off life or fun until you get to that point in the future when you're FI. Also: take advantage of being a student, of grants or programs through which you can travel cheaply or for free. Those experiences will probably be worth more long-term than saving a couple thousand while in college. (Especially if you plan to take a super-high-salary job and work for as few years as possible before achieving FI, 3K will be nothing.) Just remember you'll be a different person in 4 years: reaching FI ASAP may not be your most important goal, maybe you'll have passions that aren't extremely lucrative, maybe there will be a partner who's plan you want to consider when making your own. And that's totally fine, and don't worry about things ending up completely differently than you might have thought, I have no doubt it will be a great path regardless of where you go from college.