[Jtsummers]

At the start ask people to raise their hands if they have something to say, or make explicit points within the presentation for others to speak. If you're presenting on, say, a technical topic and the presentation (if in prose form) would have multiple sections, stop after each section and ask if anyone has anything to ask. Give them a chance to ask their question, and then take over again.

"What about X?" "Oh, that's actually going to be discussed in a few minutes." "What about Y?" "That's a good question but beyond the scope of this presentation, we can talk about that at the end if you'd like." "What about Z?" "Well, with Z ..."

But the critical thing is you only give them a chance to ask a question, and make that the format. Don't open it up to random side thoughts because then they will take over, "Well, actually with Foobar 3.0..." You've lost control at that point. If it's going to turn into a conversation between you and the person and will derail the presentation, move it to the end of the presentation.