If you’re presenting a topic, you need to be an expert on it. If your audience gets the idea that they know more about your topic than you do, you’re in trouble. By far the worst class I even taught took place when I was pressured to teach a class on Microsoft’s Access database even though I knew next to nothing about it or about databases in general. Every one of my students knew more than I did and knew that they knew more than I did. It was awful. I had zero credibility and my boss should never have put me in that situation.
If you can help it, only take presenting assignments when you already have a good background in the topic. If you don’t, make sure that you have time to do some research. Saying yes to a presenting assignment where you’re likely to fail isn’t going to do you or your audience any favors.
Taking questions after a presentation where you don’t have much depth of knowledge can be especially dangerous. You might want to consider not taking questions or bringing along someone else who can act as an authority and provide answers that you can’t. As trainers we’d rely on this strategy a lot when groups like HR or Accounting wanted us to do training on their systems, but there was no way that we were going to be able to become experts on HR policies or accounting rules. In these cases it never hurts to have backup.