Signals themselves can be a cause for disruption. Therefore, make sure signals are purposeful and recognizable, but subtle enough not to distract the whole class.
Plan ahead about how to respond to misunderstandings. Keep notes and determine which misunderstandings are appropriate to address during and after the lesson.
Props are objects that students can use in the classroom in lieu of physical signals. For example, students may raise a pencil to denote the need to sharpen his or her pencil.
Dry erase boards, index cards or colored-coded signs that are held up simultaneously by all students to indicate their response to a problem or question.