GMAT tests you on your Reading Comprehension ability. Roughly 1/3rd of your verbal content is RC. There are at least 3 passages given in GMAT verbal section and these passages can be from any topic. You need to read the passage in order to understand the context, identify the main idea of the passage and appreciate features such as the author’s tone and attitude and the organization of the passage. With every question you encounter, you need to scroll back to the relevant point in the passage.
There are long passages that run to 5-6 paragraphs. There are passages that are mid length, around 3-4 paragraphs long. And then, there are one paragraph passages that are in the short category. There is no relationship between the length of a passage and the difficulty level of the passage. Similarly, a long passage might have just 3 questions following it and a short one can have 5 questions.
The shorter paragraphs take less than 2 minutes to peruse. Allow a minute in your time budgeting for each RC question. Here again, note that there will be questions that can take more or less than the budgeted time. GMAT passages are lifted from scholarly works and are then edited a little to suit a pre framed format. This is why you can be assured of finding the main purpose of the passage in certain places of the passage. There may or may not be a definite and explicit conclusion in each passage. Sometimes, the conclusion, along with other information can be inferred from the other information presented in the passage.
Answer the questions according to the information from the passage. Do not make use of real world information you are aware of. Even if you are very aware of the topic discussed in the passage, stick with the views of the author and what he says about the topic rather than let your biases dictate the answering part. Let’s say you are a proponent of the string theory while the passage states otherwise. Forget everything about string theory when you read and answer the questions from the particular passage.
In GMAT, 80 per cent of the questions are from 20 per cent of the passage: the first and last paragraphs of the passage. So, emphasise on these two paragraphs the most when you read. You can just glance through the rest of the passage.