If you've been a part of our Thinking Strategies training, you've done an activity using a piece of text called, The House. In this activity, we ask you to read the text and underline what's important. Then we ask you to read the text again, pretending you are the parent in the situation--box in what's important. Next, you read the text as if you were a Real Estate agent getting ready to list the home--star what's important. Finally, you read the text as if you were a burglar, casing the joint--highlight what's important. This activity always drives home the point. How do you know what's important if you don't know your purpose for the reading?
Start small with your students, with a single purpose. For example, highlight any vocabulary you aren't sure of or highlight any place you are confused and write a question. Eventually, your students will be able to annotate for a couple purposes at a time.
Start with your purpose phrased in the form of a question. The brain always seeks patterns and what's the pattern to a question being asked of us? We try to find an answer. If your students are reading with your question(s) in mind; they will read to find the answer(s).
Model, model, model at the beginning. Our students don't come to us hard-wired to do this. We not only need to show them how to Determine what's Important in the Text, we also have to show them what our expectation is for the completed process. What's your Success Criteria? If your students had to rely solely on themselves (no input from you), would they know they had done a good job of annotating when they are finished?
I'm linking a great video from Teaching Channel that shows a Question being used to set the purpose for determining what's most important in the piece of text the students are working with. It's called Keep It or Junk It.
Also linked are attachments to two different rubrics that are good starting points for your success criteria for annotating to determine importance.
Next, there is an article on how to teach annotating to your students.
Finally, there is a link to an excellent lesson on Determining Importance from the Engage NY lessons.