how to improve RC accuracy from 50 to99?

i have been working more on my RC session but I still get 50 50 accuracy? what can be done, so that i can improve my RC accuracy? whenever I practice RC for the most of time i can able to understand the passage, but making my own assumptions to the author's position and making mistake in questions like strengthen and weaking of the passage and some of the inference question? what can be done to avoid it? and i also have doubt in question like what the particular line in passage refer to or why the author include those lines in passage. how to understand those lines from the passage to attend those particular questions? and what can be done to improve accuracy at para jumble questions