One art which I am still mastering is that moment at the end of a talk, when the chair gets up and announces 'OK, we'll open it up for questions and discussion'. Some people's hands immediately shoot up, and they make their point with confidence in relaxed style.
For me, putting my hand up can be a nerve-wracking affair. You have to wait until it's your turn, rehearsing the question over and over again in your mind. And the thought process is often 'What if this question sounds daft?', 'Maybe they covered the point I'm asking about and I missed it?', or 'Maybe they explained X clearly, and I'm the only one still left thinking about it.'
And then, even more frustratingly, sometimes you have your question, go through the thought process above, conclude it's not worth asking, and then somebody two rows in front asks the very same question. 'But that was my question' you think.
So now, if I have a question, I'll usually ask it. The more I ask, the more confortable it gets. If the talk is on a topic I know very well I might make a comment, but most times, I prefer to ask a question when the presentation itself raises a question that I want an answer to. And if at all possible, I keep my question succint. As Eugene Delacroix said, "Artists who seek perfection in everything are those who cannot attain it in anything."