Simple, yet sophisticated, AfL (Assessment for Learning) questioning technique to help teachers move from good-to-outstanding. It also helps address differentiation in the classroom and encourages teachers to take risks.
This is the hard part.
Many, many teachers are very reluctant to hold onto a question or a stumbling block in class. I know because I have done it; but my greatest lessons are often the ones that involve the ethos being established from the outset and (me) not being afraid to tease out "why?" student A or B thinks the way they do...
Ensure that all your students understand a concept. Test it before moving on. Try it tomorrow. Don't accept student E or student K shouting out the answer to maintain pace or behaviour. Don't allow student T to answer the question because (you know they won't let you down and) they will help you move on during an observation lesson!