Wondering about college...

So… I’m a junior in high school, and am just starting to look at colleges..(and Im not quite sure what i want to go into… (medicine, biology….somewhere in the sciences at least). ) I was wondering, what happens when I get accepted by a college? Do I choose my schedule ahead of time, like in high school? Do I choose when I go to the school for the first time?

And also, is there some kind of aid that will help me fly to different schools across the country, and see how they are? If not, how am I to see what kind of schools they are, and see if I’ll fit in, without having to spend a fortune on travel? \

Another thing… what sites are out there for me to find scholarships?