What do you feel are the critical principles of good software engineering?

This is a general question that asks you to characterize what makes a software program efficient and effective. Your ability to do this will help the interviewer at Google understand your qualifications for the position. Your answer should incorporate both the requirements for the job - as stated in the job description - and your previous experience writing code. You should limit your answer to 2 to 3 important principles and anticipate a follow-up question from the interviewer.