How do I get into Dartmouth College in Hanover New Hampshire?

Hi, I'm a freshman and I really want to to go to dartmouth in three years (I understand so do thousands else). My grades need improvement, and I currently have no extracurriculars since I was just booted from rowing, but this is something I really want. So I was wondering, great users of yahoo, what can I do to perfect my application, and even if I improve my grades, since I slacked off most of freshman year (As to Bs, not my typical all As) do I even still have a chance? I'd also appreciate some suggestions to improve my grades. ----Thank you!