Thorough analysis of official questions that you got either wrong or correct helps you in identifying patterns that would prove gold in the long run. Now that is the learning we get by solving those official problems and that is why everyone emphasizes their importance.
By official questions I mean, OG13, Gmat prep and Gmat prep question pack 1.
For CR :
We need to focus on at least three kinds of patterns
Why an answer choice is wrong instead of just saying it is out of scope ! Powerscore provide you with solid concepts that deals with characteristics of both wrong and correct answer choice.
Why an answer choice is right
type on reasoning used in the stimulus