 This idea for teaching the past perfect continuous tense is simply an adaptation from the same idea used to teach the present perfect continuous tense. Here now, we'll have a student come up in front of the class, receive a certain prompt, make an announcement, and the rest of the class will guess as to what the person had been doing before something else happened in the past. Now here, yesterday you were crying because you had been watching a sad film. Our student would simply come up, read the prompt, correctly as, yesterday I was crying because, and allow the rest of the group to guess as to what was happening. Some example guesses may include, you were crying yesterday because you had been fighting with your boyfriend, or you were crying yesterday because you had been chopping onions, so on and so forth.