I applied in-person. The process took 2 weeks. I interviewed at Caltech (California) (Pasadena, CA) in Jan 2011
Interview
I found my mentor after hearing a lecture he did, emailing him without a response, and ultimately knocking on his door and requesting a research opportunity. Then I was interviewed by a graduate student that I would be working with, if selected. SURF also required an online application once the professor agreed to sponsor me.
Interview questions [1]
Question 1
Most of the questions were behavioral, but the more difficult questions were about matlab algorithms I would try to use for specific image processing tasks