The "3-2-1 rule" is a guideline for effective presentations and communication. It suggests that for every slide or key point, you should include no more than three main ideas, two visuals, and one takeaway message. This approach helps keep the audience focused and engaged, making it easier to remember the information presented. By adhering to the 3-2-1 rule, speakers can avoid overwhelming their audience with too much information. This method is particularly useful in settings like business meetings, educational lectures, and public speaking, where clarity and retention are essential for effective communication.