Write a list of passages or references on the board that have something important in them -- something "worth underlining." Explain to the class that there is something important in each verse and that you will give each student a chance to read their passage and explain to the class what they thought the most important thing was in the verse(s). Give them a few minutes to look over their passage. Go around the circle (if your passages are in order) or use Delilah to choose the next person to share what they felt was important. Remember to prompt students to share their ideas: "Why did you feel this was important?" I sometimes say "That's what I underlined, too! What did you love about this passage?"
Once your students have done this once or twice, you won't need to give them time to read the passage ahead of time. They will be able to identify the most important things in a passage cold -- a valuable skill for future teaching or missionary work.
I have found that after a few students read scriptures and talk about what's most important to them, suddenly all the students in the class begin marking their scriptures as well -- even the passages they weren't assigned. In fact, one year I had students write in their scriptures the names of the person who shared the scripture with them. A missionary shared the passages online a few weeks ago and how much it meant to her to remember the testimonies of her Seminary classmates.