If I was going to implement a lesson plan, I'd let the kids know what our goal was. I often do this on the board daily. The list may include paperwork (collection or distribution of graded paper), review of the highlights of what we covered the day before, and then either a specific goal or a goal-setting question. I always think it's best to give the kids some idea of where you're going, but I don't know it's necessary to give the entire thing away, so a general approach might work best. Ask a controversial question and suggest a discussion if you're trying to explain, for instance, concensus. I might ask the kids to tell me what they know about Shakespeare, or for Macbeth or Hamlet, I'd ask what do they know about ghosts, have they ever seen one, do they believe...We might spend the lesson on the supernatural, but I might not connect it to Shakespeare until the end of the lesson as I'm introducting that aspect of Elizabethan drama. But I would tell the students that we were going to discuss our preconceptions about the supernatural, and that would be an explicit expectation. It would be open-ended enough that it should pique their curiosity, though they might not necessary connect Shakespeare to it. By the end of the lesson, everyone would have shared what they knew, learned some new things and eventually have found out that the supernatural was really popular in Shakespeare's time.
If something was to be accomplished and graded by the end of that period, I would give directions, examples, answer questions, and tell them exactly what I wanted completed at the bell. I might close out their time 5 minutes before the bell to avoid chaos. In this kind of situation, I might even announce what we were going to do, the previous day.