In order to do well on Reading Comprehension questions, you need to be adept at reading a variety of passages, have a decent reading speed, but most importantly have good grasping ability. Unless you understand the content of the passage clearly and accurately, you will not be able to answer more than 50% of questions asked.
As you practice, try different approaches to reading the passages. Alter the pace of reading, re-read some portions for better understanding, etc. Try to narrow down to a reading style and approach that works well for you and stick to it.