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Okay, RC from the beginning. You mention that you have used our "basic vocabulary guide" - are you talking about our Foundations of Verbal book? If not, I would start with that book. It has lots of good information on how to break down complex sentences, plus it has about 75 pages of both vocab words and common RC expressions / idioms that will really help you. (And if you have only done the vocab portion, go back to that book again - do the other parts as well! Getting better at SC and CR will help you on RC, because all three question types are still about reading and deciphering sentences.)
Next, you're going to need to start reading regularly - a little bit every day. Start with things like The Wall Street Journal, The New York Times Magazine, and The Economist. As you feel more comfortable, read Scientific American.
You can also check out articles from these two sources:
http://magazine.uchicago.edu/http://harvardmagazine.com/Some of the articles from the above sources will be too casual but others will be exactly what you need. If you start reading something and it feels too easy, just stop and go find something else to read.
As you feel more comfortable over time, skip the first 1 or 2 paragraphs. Read 3-4 paragraphs and see how much you can pick up about the main ideas and messages, then go back to read the first paragraph (or first two paragraphs) and see how much you were able to get.
When you read, take very light notes - the same way you would on the real test. Your goal is to find the main idea of each paragraph - that's it.
If you've got a friend who is very good at RC, you can ask him or her to read some of the same things. You can write up short notes for the main idea of each paragraph and ask your friend to check your understanding.
If you run into a sentence or paragraph that is very confusing, try to explain it as best you can and ask your friend to correct you - to tell you what s/he thought and HOW s/he knew that this was what the sentence or paragraph was about.
Finally, you're going to need some kind of specific resource that will help you learn how to do RC - in the same way that our SC guide is helping you with SC.
One other thought: you may want to seek out a class or other outside help (besides working with a friend). I have an obvious conflict of interest in recommending this (since my company offers classes and tutoring), but it is still one possible path, so I should mention it!
And, last but not least, here are a few free resources:
Improving your reading skills:
http://www.manhattangmat.com/blog/index ... rehension/How to read RC:
http://www.manhattangmat.com/blog/index ... p-passage/What to read and what not to read:
http://www.manhattangmat.com/blog/index ... -passages/http://www.manhattangmat.com/blog/index ... -passages/