Text book reading and reading for pleasure is two very different things. There are several things that I do to help me distinguish what is important.
When reading a text book the first thing I do is read the title. That can normally tell you something about the text you are going to read. Then, if it is a text book, I will read the headers in the chapter. This usually tells you the main points and focuses of the chapter. I then look over any questions that might have been outlined in homework, on the syllabus, or raised before we left class. Then I look over the notes that I took in class and look for that in the text. Then I know I read what about what we are covering in class. I want to know why I am reading the text, so the last methods really help me see the purpose in what I am reading. It helps me to know that what I am doing matters. I may also highlight anything that I feel sums up what I have just read, whether that is in a section under a specific header or chapter. I especially read carefully the introduction and summary. That way I have an idea what I am going to read, and some of the main points that I should have taken away.
Internal communication happens more at the end. That is when I ask myself if I understood what was read, do I see what the teacher or professor wanted me to see, or do I understand the main points. Internal communication, for me at least, happens more when I am reading for pleasure, because I do not care if the questions in my head distract me from what I am reading. I dont want to get distracted when I am reading something for school.
Texts are many times unclear, especially school texts. Many times I feel I get lost in the language, however, I feel that I still have good ideas on how to address the texts. Even if I dont always know what is the most important thing to draw from a text.