What most people are saying is correct - many/most people have no idea what they wish to do when they 'grow up'. Those around you, the young people, I mean, often choose something, and then put that label on themselves so they can show the world that they've 'decided'.
One other thing - you'll change as you get older - and your ideas about the world and your place it in will change as well (this in itself is a very GOOD argument against tattoos - you'll change, but that mark on your body will still be there...). Even if you had very clear ideas of what you wanted to do now, they would very likely change in the future. I had friends in college who were 'sure' of where they were going - only to have a mid-life crisis later on - and go to something totally different.
I'm 42 now - an age I could never see myself at 'that age'. My father (a very successful cardiac surgeon) used to tell me that if I could not figured out what I wanted to do by the time I was 40, I would be in real trouble. When I turned 40, it was kind of a relief - I just said '...Oh well, I guess by his standards, I'm in trouble... Now I can figure out what to do with the remainder of my life...'
None of this is to say that you should just blow it all off and party, however. I was in a fraternity in college - and spent most of my time chasing girls and keg parties - time that now (as a 42 year old) I see as not 'wasted' but - also 'not very smartly spent'.
You should have a good time while you're in school - but also be aware that you're configuring your skill sets for when you hit the work world - and as such, you need to load yourself with the best possible tools you can. Once you get out here, no one really cares about you or what you do (occupationally) anymore (like they do when you're in school).
So - what to do? Well, try starting out by going to your career counseling center. Take an 'Interest Survey' test - a very long, boring test, which will tell you where your interests are. I had a fraternity brother who took this test, and one of the things it told him was to consider being a funeral director. We all laughed at that - but you know what? Today he owns one of the largest funeral home chains in FL - and he's worth millions.
Second - determine what your strengths are - with respect to your intellect. You should consider arming yourself with VERY BASIC VALUABLE skills that most kids shy away from. This means things like math, engineering, medicine, etc. Consider this your opportunity to learn skills that YOU WILL BE ABLE TO FEED YOURSELF WITH AFTER GRADUATION. If you want finance, etc - then do it as an MBA - you'll be worth MUCH more. Basic skills first - more specific second.
Basic, non-sexy skills are the way to go as an undergrad. The world is full of poli-sci majors who work for fast food restaurants - and believe me - I know - I was a 'communications' major - my first job after graduation was as a bank teller in San Francisco! Talk about a rude awakening....
Anyhow - that's my rant. You'll be ok - try not to stress. Just don't waste tons of time doing nothing either. You'll find that life goes by VERY FAST. Before you know it, you'll be 42 like me - wondering where it all went.
Good luck -
//sse