One of the best ways to raise your reading score is to read fairly quickly-- for a purpose.
The ETS reading passages were chosen because of their discourse-- the author's logical reasoning, how the author makes his (or her) points.
That means that an important tactic for test takers is to predict what will be TESTED before the questions. Then, when you are skimming through the text, look for the logical points and categories. For example, if
the author says, "there are two types of carnivores..." , chances are that will be tested, somehow, someway. Perhaps in the chart questions.