[Cd00d]

Lots of great advice here, but I want to add something tangential to some of the points, which is less important in a presentation than a meeting.

Own your ignorance. Nobody knows everything, and the people that are confident are the most comfortable saying "I don't know" "I don't understand" and continue on with questions until they do comprehend what's going on.

There is likely no room that you're in where if you have a question or don't understand you are the only one. State your ideas, ask your questions, and the room will be better for it.

Also, I will sometimes ask a wrong-headed or obvious question on purpose to gauge how reliable/knowledgable someone else is. Saying something that gets shot down or criticized doesn't necessarily mean the speaker should have less credibility. It's also good practice to get comfortable saying "I don't understand".

Good luck!