One area where a lot of presenters fall down on the job is Questions and Answers. When you are preparing your presentation, be sure to plan for Q&A. And plan well in advance!
While you are rehearsing your presentation, give some thought to questions that your audience may ask. Are there any complex topics that some members of the audience might need clarified? If you have spoken on the same or similar topics before, what kinds of questions have previous audiences asked? If possible, show your presentation to colleagues, and get their input on possible questions.
When the time comes to do your presentation, be sure to allow time for Q&A. Some presenters are comfortable taking questions throughout the presentation but many would prefer to take questions at the end. If that is your preference, announce up front that there will be a Q&A at the end of the session. If someone jumps the gun and asks a question before you are ready, just thank them for their question, and promise to answer them in the Q&A session at the end of the presentation.
During the Q&A session, listen attentively to the question, then restate the question with words like, "So if I understand you correctly, you would like to know..." This serves two purposes: it ensures that you really do understand the question, and it also ensures that any of your audience who didn't hear it will also know what the question was.
Try to keep your answers short and to the point. Don't let one questioner dominate the Q&A session; make sure everyone who wants to ask a question gets a chance. If the question is way outside the scope of the presentation or is going to take too long to fully answer, invite the questioner to stay after the presentation for an off-line discussion.
If you don't know the answer to a question, be honest. You may offer to find the answer, and you can invite members of the audience to leave an e-mail address, and you can send out the answer when you have found it. (A great way to collect some leads!)
Don't go over the time allotted for your presentation. If you are near the end of your time, and it looks like there are more questions, invite anyone who wishes to stay after with questions. This is probably a good idea in any case, since there will always be a few with questions who were just not comfortable asking their question in front of an audience. I always like to offer my e-mail address in case anyone has a follow-up question.
Finally, don't just end your presentation with the last question. That is a weak ending. Prepare a few closing remarks, and even a slide or two to wrap things up.
With a bit of planning, the Q&A session can be an effective part of your presentation.