You've probably all seen TED talks. They are typically very well done.  TED has a column on what makes a good talk.  

Why do some TED Talks rack up millions of views, while others on similar topics get less attention? 

• “It’s not what you say, it’s how you say it.” People rated speakers comparably on charisma, credibility and intelligence whether they watched talks with sound — or on mute.
   
• “Jazz hands rock.” There is a correlation between the number of hand gestures a speaker makes in a talk and the number of views the talk receives.
   
• “Scripts kill your charisma.” Speakers who offered more vocal variety showed better ratings on charisma and credibility. What’s especially interesting: people rated speakers who clearly ad libbed in their talks higher than those who stayed on script.
   
• “Smiling makes you look smarter.” The longer a TED speaker smiled, the higher their perceived intelligence ratings.
   
• “You have seven seconds.” First impressions matter a lot. People had largely formed their opinion about a speaker based on the first several seconds.