Don’t leave questions to the end. Don’t talk at your audience about your passion - and exclude them. While they sit waiting for you to stop, who know’s what they’re thinking? They may be sitting there appearing to be at the presentation. They may be tweeting away about football.
When you’re in conversation with an individual, you can fairly easily tell when their mind is wandering, when they’re just being polite.
Don’t present from your little world. Engage… Engage… Engage… Never forget that every person in the audience wants you to engage with them. And if the topic is "social media", they’ll judge the value of your words by your behaviour.
It can be really good to begin with AOB - the questions.
(1) Start with winning rapport - without this you are lost
(2) You can win rapport by showing that you are genuinely interested in your audience
(3) A great way to show you care for your audience is to ask them what their questions are.