As I read I pay attention to the main points in the readings. I focus on the points that are the central part of the readings. The points that everything else is focused around. As I read I focus on the first couple of sentences and the last couple of sentences in a paragraph. I think that will give you the main points and the points that are the most important in the book.
When I am reading I think try to constantly be thinking about how everything is related so I can fully understand the text. I like to think about the topic and I try to focus very intently on that so my mind doesn't start to wonder. Sometimes when I read I read a word and it triggers a memory of a past experience and my mind starts to wander. When that happens I have to go back and read everything I just reread trying to focus on actively trying to relate everything I'm reading.
One thing that helps me to know what is important is by reading what the first sentence of a paragraph is about. I think that will give you a pretty good overview of everything you need to go over. As I read I try to use a highlighter or take notes because it helps me to remember what I have read. It also makes it easy to go back and recall something that I have read. I usually remember where it is better when it is highlighted or in notes.