Great advice from John...if you are looking to understand what the top-tier undergraduate business programs are, then going to the Business Week rankings is certainly a helpful place to start your research. Once you've identified a few programs that interest you, you can go to their specific sites in order to learn even more. To echo John's point, as part of your research, I'd also spend a bit of time thinking through what area within 'business' you are interested in, as certain schools will specialize moreso in Finance, Marketing, Accounting, etc.
Would also recommend that you work with someone at your school (Career / Guidance Counselor) to understand what schools might be a good fit given your GPA, SAT Scores (and your ability to pay for school - some programs can be a much better value - whereas others might be more expensive than they are worth).
Lastly, when rereading your question, thought you might also be interested in understanding ways you can prepare for college business programs while still in high school...not sure if I've got it right or not, but I'll share a few thoughts on that as well.
If that's the case, if you are interested in understanding how to prepare for business programs while still in high school, I'd recommend that you try and take a few relevant classes on business topics before graduating. As an example, does your school offer an accounting/bookkeeping or economics class? If yes, those classes would be very helpful for you. Also, does your school have any links to Junior Achievement? Organizations like JA often partner with schools to provide classes on business topics, particularly entrepreneurship.
Hope that helps...good luck to you!