How do I know if all students are paying attention?

In Attention, Meaning & Mastery I wrote that all teachers need to answer four questions every lesson:

1. How do all know that all students are paying attention?

2. How do I know that all students have made sense of what has been taught?

3. How do I know all students are mastering the skills I want them to learn?

4. How can I do all this in a way which is inclusive and results in all students experiencing success?

This post will go into more detail on the first question.