I gave a presentation today to a group – not the group pictured here, but a similar industry group, and as I was thinking about the talk and how I will prepare for the next one, I was struck by a few axioms that I often forget in the moment and that seem like great reminders for my next talk.
1) You are the expert on your subject, but you don’t have time to tell everyone everything you know — it matters more what the audience feels. When I spoke today I noticed a few head nods, a few confused looks, and a few scowls. I want to get to all head nods, smiles, and fewer scowls, but that might not be possible with this subject material. Goal for the next talk: frame the talk even more in the language of the audience, not just in the language of the product.
2) People need to be reminded and encouraged to ask questions. The audience can be shy — having a ringer in the audience to ask a question can get them going and it’s always good to ask them questions even when it looks like none are forthcoming. Goal for the next talk: ask a question after every segment of the talk, and get answers from the audience.
3) Have fun! People see when you are having fun and it’s infectious. Goal for the next talk — enjoy the opportunity to engage with a group even more …
Information Maven 
Those are very good points to keep in mind. I can totally relate to what you mean by speaking the language of the audience. I think the hardest part for me is the preparation. I have a talk coming up and I plan to use mind mapping to help me get my thoughts on paper to deal with that particular challenge. I have found Toastmasters to be very helpful in this regard and in general with regard to helping me become a better communicator.
Agreed….watching TED talks, and things like this…people love listening to people that are having fun at what they doing, and making the audience laugh at some point in the talk goes a long way.