Here's a rule of thumb assuming that your audience is neutral about your topic. Only 10 per cent of your impact is in your content - 90 per cent is in how you deliver the content. Much of that 90 per cent is in your body language. if you ignore that, you're neglecting a fountain of natural, built-in credibility. Try this mental exercise:
On the face of it, it sounds absurd: surely the answer belongs to the person who asked the question. But in a group that’s almost never true. Subconsciously, the entire audience adopts the question as if every person had asked it.