Hand out sample annotated texts to students, and have them read the texts and the notes. Have pairs of students discuss the purpose of the annotations and how the editors are using them to help the reader understand the texts.
Discuss the texts as a class. Have each pair of students tell you the functions they thought of for the annotations, and make a list on the board. If students are stuck, demonstrate how the annotations help clarify difficult vocabulary, make references to other works, give cultural or historical background and help readers notice unusual stylistic choices in the text.
Have students take out the Shakespeare play you are studying. If you are not studying a Shakespeare play at this time, hand out a page or two from an annotated edition. Also hand out copies of an annotation guide such as the one by Read Write Think.
Have students read a page or two of the Shakespeare and look at the annotations. Ask them to note which function from the Annotation Guide each note serves.
Assign students a scene or two of the Shakespeare for homework. All students should read the same material; each student is individually assigned a page to annotate. Have them research unfamiliar words, mythological references and historical references for their annotation, and have them explain complicated ideas or draw parallels to modern or personal situations.
Have students trade annotated pages in class the next day. Each student should read his partner's notes and mark which ones were most helpful to him in understanding the material. Students should then receive their own papers back and see which of their notes were useful and which were not.
Give students the opportunity to revise their annotations, editing out the ones that their partners did not find helpful and adding new ones more similar to the notes their partners did find helpful. Have them again trade papers the following day and see whether their partner now understands more of the text.