What's your strategy? Do you read the questions first and then read the passage. Do you scan the passage or fully dive deep into it?
I had an issue with RC as well, however, over time studied what worked for me personally - which will differ for everyone. I found that looking quickly at the questions gave me a better idea of what I needed to pay attention to as I was reading. The best advice I can give you that worked for me is read actively. Pretend that you are truely interested in the material as it will engage your mind and thought process.
Other strategies that people grapple with are whether to answer passages with more questions or to go after ones that they will have scanned and picked out the ones deemed "easiest." It's something that you'll have to work with using practice tests to determine what your most efficient method is.
I would also suggest that you take a couple practice tests with two RC sections as God only knows what type of experimental section they will throw at you. You'll not only give yourself more practice but train your mind to cope with the specific fatigue that become of multiple RC sections.
In a nutshell, develop your own strategy with PRACTICE.