Giorgio,
I also had lots of trouble with SC in the beginning, but SC is now the easiest part of the test for me. I do attribute my increase in SC because of MGMAT. I've seen lots of other strats and MGMAT has to be the best.
First, practice practice practice!. I don't know how you are approaching your studies but here's what I did. I practiced each problem type, over and over again, until it became second nature. I would take an active approach to SC, correcting sentences as I read it by identifying the subject of the sentence, looking for tense and predicting what the tense, pronoun referent etc. SHOULD be in the sentence. It's much better than being passive about SC and reading sentence after sentence. This way will just confuse you.
After you are comfortable with the strategies, reinforce what you learn by looking for the problem types in questions that doesn't have that specific problem. That way you're reinforcing your foundation. Most SC questions combine 2 or 3 problems in one question so don't panic, if you can find correct one error, look for the answer choice with the error corrected, and if there's 2 questions that are the best candidate for the right answer, compare the two. After you've memorized all the strategies, SC becomes intuitive and less mechanical. In addition, every question I've ever done has taught me something very distinct about SC, so I make a cue card about that question and review it. I also have lots of different sources for SC so I don't run out of questions. Also, I would refrain from watching lots of TV, because that's where all the worst sentences come from. I'd watch documentaries because they're more informative and more likely to have better constructed sentences than your everyday TV show. T
RC is a little more tricky, it is the hardest thing to improve. I notice that the passages I do best on are historical or political because I was a Social Science major. Best thing to do, is practice! I spend about 20 minutes everyday reading things that I would normally not read, for instance Scientific American, or the science section in the Economist. This way you become more familiar with reading passages that contain words/terminology that you are uncomfortable/unfamiliar with. By doing this you're toning that "Reading section" part of your brain and making it a habit to constantly absorb information.
Also on reading passages on the test, I map out the entire passage and not read the first question. You don't want to approach RC from a question by question approach because then you are scanning for that question only! This will take you more time than if you read the passage correctly once. This works for me because when I write down the passage in point form, I remember it better than if I were just to scan it off the screen. This also helps for organization questions because I have the whole organization in a way that I understand it in front of me. I only refer to the screen for very specific detail questions. It does take a while to get used to it, especially knowing which pieces of info you should write in your notes and what you should exclude, but again practice practice practice. That first RC question WILL take me 4-5 mins to complete because I'm paraphrasing the whole reading passage, but every question after that will take me 30-45 seconds!
RC questions can also be tricky because the phrasing in the questions can be very deceptive. I don't know if you're a native speaker of English, but look at each word in the question types and try to get its implicit meaning. For instance if the reading passage is summarizing a policy or plan, then any question asking for the purpose of the passage that does not include "policy, plan" or calls it something else that is not related to plan is obviously wrong!
Hope this helps. Good luck in your studies.
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