Improve scoring of the Reading Comprehension

follow below few points that have helped me (and might help you also):
1) dont time you RCs in your starting phase...read slowly and understand the passage thoroughly.
2) read 4-5 articles daily from economist.com and nytimes.
3) build your vocabulary.(make a note of all new words which you encounter.)
4) make a habit of practicing RCs on daily basis.(4-5 atleast).
5) make notes of those points which you feel is difficult to understand(this will reduce as you practice more).
6) analyse each RCs thoroughly after you are done...dont leave after attempting all question..as by doing this you will figure out where you went wrong.
7) practice as much as possible.

GMAT RCs VOCABULARY LIST: vocabulary-list-for-gmat-reading-comprehension-155228.html

hope it helps.