Most of the work you do to solve a CR or RC problems should happen up front. Do you understand the passage/argument? Do you know clearly what it is asking you for? Have you tried to predict an answer? (You should be able to predict, at least in rough terms, on the majority of CR/RC problems. If that's not happening, you are moving to the answer choices too soon.)
I also strongly suggest that you avoid focusing too much on incorrect answers. Sure, it's important to learn from your mistakes, but if you simply focus on the little wording difference or loophole you missed, you may fail to see the overall point. You should review
every problem you do to see if you could have solved more efficiently. There are four parts of your process to review:
1) The initial read of the argument or passage. Did you read efficiently and accurately? Are there important elements you missed or (especially in RC) areas where you spent too much time reading?
2) Interpretation of the question. Were you able to quickly identify what the question was asking for? Did you know what to do to find an answer?
3) Prediction. For an Assumption Family CR, were you able to identify one or more flaws in the argument and make a prediction that matched the specific task (e.g. Weaken, Evaluate)? For RC, did you identify the right part of the text to draw from? Could you have found this faster? Did you have a strong sense of what the answer should look like? Did your prediction match the right answer? If not, is it because you were wrong or because there were multiple possibilities and the correct answer went another way? If you didn't predict the answer, would it have been possible to predict? How?
4) Answer choice analysis. What makes each of the four wrong answers wrong? How is the right answer different from the others? Is there a subtle difference, or is there some very clear difference that makes the right answer right? Were there traps that pulled you in the wrong direction? For instance, maybe a few of the wrong answers seemed relevant when they weren't, or maybe there was a subtle term switch you missed, or maybe the right answer seemed flawed in some way? How could you have bypassed these problems more efficiently?
This is just a sampling of the work you can do on a problem. If this seems time-consuming, it should be. You should spend far longer reviewing problems than you spend doing them! That's how you learn to do things differently. Good luck!