here is how i think it is done:

a. go to ratemyprofessor.com before you sign up for a class (or within 1 week of class)

b. on the first week talk to your proof about his philosophy of teaching and grading. Ask him/her specifically what % of students get an A in his class. Also let him know that you are pushing yourself to get all As (dont sound like a hardass, let him know its your resolution or something). and listen patiently for any volcano eruption or genuine suggestions - whatever happens to come as a response.

c. dont let your words from b go to waste, show by actions that you are infact planning on getting an A.

d. talk to your proffs regularly,

e. (controversial) if step d is successful he will be going out to local bars with you by next month.