Hi, few days ago I barely hit Expert on Codeforces, I would like to know the best strategy to stick in the Expert zone, and also the practice strategy to become Candidate Master. I usually solve Problems A,B and C. I sometimes do D and E outside of contest. Usually, their ideas don't strike me, but when they do, there's very little time left in the contest. How to reduce that time of striking ideas ?

Also, what should be the best strategy for upsolving the Google Code Jam problems ?