According to Speaker Rich Hopkins, you can do Question & Answers throughout your speech if you:
- Give the rules - make it clear at the beginning of your speech how people can ask questions (e.g., note cards, twitter, upraised hand, etc.)
- Control the flow - take questions when there is a natural break in your presentation - acknowledge questions with a glance or gesture and answer them when you get to your break
- Cue the close - just before you reach the climax of your presentation, let your audience know you are taking no more questions during the session (although you could take them in email or after the session) - then deliver a powerful climax to your speech
Tim Wilson
Professional Speech Coach
Free speaking tips at: http://speakingquicktips.blogspot.com