When/how do I apply to Haas?

I’m applying to Berkeley, and I know that they have a great business program at their Haas school. However, I also know that I can apply to Haas two years after entering the school. But I have a couple questions.

Currently on my application, I’ve put down Economics as my major. Can I go in as an Econ major and be able to decide the classes that I take that are prerequisites for the Haas program? Or do I have to go in undecided or something and do the Haas classes first?

Thanks!

For students who entered Berkeley as frosh:
http://www.haas.berkeley.edu/Undergrad/ucb_admissions.html

For junior level transfers from other schools:
http://www.haas.berkeley.edu/Undergrad/transfer_admissions.html

I know little about the process for continuing UCB students, but I would guess that both Haas and econ require a lot of the same pre-reqs. Considering most that don’t make it into Haas go the econ route, that would make sense.