Ventivish gives good advice. I won't describe the whole RC method here -- it IS our business and our product, after all -- but there are a couple of points I'd like to make.
First, the "points system" mentioned in the first post appears to be an attempt to provide a semi-mechanical algorithm for finding the "right answer" without having to think too hard. This is a waste of time: The whole point of RC, especially the "global" questions such as purpose and main idea, is that you have to understand the fundamental, central content of what you are looking at. Your first task is to see what the author's REAL main point and underlying purpose are. That means thinking. Looking at keywords and first sentences of paragraphs can help, but they are only clues. Actual understanding is what counts.
Second, "close reading" as you would do in CR is not a good idea on your FIRST reading of the passage. The time when you do careful and close reading is when a particular question asks for a detail or depends on a detail. At that point, you closely read the detail and its context, not the whole passage.