Below is my approach to CR questions:

1)read the question first.develop a predefined strategy depending upon the type of question.eg,(a)for an assumption qsn, find the flaw in the argument.normally the author will assume just the opposite of flaw to hold the argument true.(b)for strengthen n weaken qsns, identify the main base on which the argument depends n attack that base.

2)identify 3 most important things of the argument i.e., premise, conclusion n assumption.

3)in ur mind, frame what could be the possible answer to the question.
this will help u in two ways -(a)with practice, for some CR questions, u will be able to predict the correct answer option.(b)even if ur answer option doesnt match with ny of the 5 options,it will help u to eliminate options which r out of scope of the argument.

4)make sure to read all the options before fixing an answer.

5)remember we r supposed to find the best among 5 options given. so dont try to find the perfect right answer for the CR qsns because most of the questions can be answered in more than one correct ways.

Thanks!

My Suggestion,
Either OG verbal guide or MGMAT Critical reasoning.