Impromptu and extemporaneous are two totally different speaking methods, yet the two are sometimes used interchangeably (as in this recent article from Associations Now). This causes confusion.
Here’s what you need to know: Impromptu speaking (also known as winging it) is always a bad idea. Extemporaneous (speaking without notes while still knowing what you want to say) is fine, provided you prepare ahead of time.
To be sure, CEOs and other executives often find themselves in situations where they must speak with little to no advance notice — anything from running into a group of employees in the break room to being asked on the spur of the moment to offer brief remarks at a professional society meeting. Experienced, skilled communicators realize the need to always have a message in their back pocket for times like these. This is how those skilled speakers we admire so much manage to turn a seemingly off-the-cuff set of remarks into a work of art. They know how to turn an impromptu request (which has high potential for disaster) into a smooth message-driven extemporaneous talk.
How can you use this advice? Whenever attending a public forum, decide in advance what message you want to leave with the crowd. If you should be asked to speak, you’ll be the one ahead of the game.