The biggest thing that seems to help most GMAT takers get better at RC is to realize that most of the details in the passage will never be directly tested in the questions. On our first readthrough, we should focus on the universal themes: the topic being discussed, the author's feelings, and the author's purpose for writing the passage. These make up the basis of many questions (you're pretty much guaranteed to see at least a couple "the primary purpose of the passage is to..." or similar), and they allow us to go back and pick out the details we need when a question makes a specific reference.