Focus on operational words like "smaller," "causes," or "first."
Here's a shorter sample from QuotEd Reading Comprehension, my company's GMAT RC app. There should be some vocab you don't know, even in this brief quote. I've highlighted some words to focus on:
"It is a difficult thing to tell the story of a life, and yet more difficult when that life is one's own. At the best, the telling has a savour of vanity, and the only excuse for the proceeding is that the life, being an average one, reflects many others, and in troublous times like ours may give the experience of many rather than of one."
Source: Annie Besant. Annie Besant, An Autobiography. 1893.
According to this quotation, autobiographies are:
A) Only interesting when they involve the life of someone famous.
B) Best told when they represent the lives of people who will do exceedingly great things.
C) A representation of an average life without any vanity.
D) Thorough demonstrations of troubled times through the experience of everyday people.
E) Most permissible when the individual narrative captures the experiences of many.
The answer is not A because this quotation is neither about interesting life stories nor about famous people. Answer choice B is disqualified by its qualifying phrase "who will do exceedingly great things." While C includes necessary elements, its definition would exclude autobiographies that are representations of exceptional lives or exhibit vanity, but the quotation merely suggests that humble autobiographies are best. Answer choice D focuses on demonstrating troubled times, which isn't the focus of the quotation (they are just IN troubled times). Answer choice E incorporates the quotation's goals for an autobiography, that it represent many or average people, while allowing for other types of life stories to exist.
So, E would be your "best" option. Hope that helps a little! The advice from the previous responders is solid, btw.
) then you will speed up without having to spend ages going through the passages in lots of detail. 
