Well,building a good speed and accuracy in RC is something which takes a lot of time and effort. I can say that from personal experience. Not that I have cracked the GMAT but that I have improved quite a bit from where I was a few months back.
The method which works for me is that one shouldn't bother too much about the details on reading for the first time.
You should be focusing on the main points so that you don't end up reading every excruciating detail of the passage.