Hi,
you can improve your RC score using the following technique, this is just one of the techniques suggested by experts...but you can develop your own strategies by doing more quality practice(more on that later)
1.paraphrase the passage - imagine you're rephrasing it to a 6 year old
2.note down function of each paragraph
3.note down shifts in tone of the author in the passage
4.understand the intent of each paragraph and passage as a whole
5.every answer choice you pick should be justified completely by the passage, not partial but complete...
by quality practice I mean, do one passage a day, but make sure you thoroughly review why you got an answer wrong...