I ask my students to take out the books and materials they are to use during the whole term. I introduce the books one by one by holding them up and presenting their titles. For instance, for a workbook I would say: " Look, this is your workbook," and have them repeat the word "workbook" after hearing it a couple of times. This activity goes on until all the books are introduced and can be recognized by all the students. So, when I say, "Take out your textbook," they know which book they will be working on.