Michael Weitz and Abigail Tenembaum, founders of Virtuozo, coach everyone from TED speakers to CEOs to express their message effectively.
"Even the same audience is different at 9am on a Monday than it is after a long day of presentations at 5pm."
That might mean throwing aside the PowerPoint, or adding in a personal anecdote if your message can go off-script.
"If you ask attendees of TED talks what drives them crazy, it's when speakers talk like they're reciting a memorised text," says Weitz.
"If you speak fast in a low voice, your impact will not be what it could have been."
"Most people will put their foot on the accelerator," says Weitz.