How to get into Caltech?

Hi, I'm from Norway and are thinking of applying to Caltech. I have all the most difficult classes (physics, chemistry, the most difficult math, and so on) and good grades. Grades are given from 1-6 (where 6 is best) and my average is about 5.4. In addition you get extra points in Norway for taking the difficult classes, though I don't think they will be accounted for when applying abroad. How do I go about applying, and is there any chance for me to actually be accepted? Thanks:)