If you do end your talk with the question-and-answer session, do so before all the questions dwindle away. Try to end with a question from the audience that restates your position. Never keep going until some people are putting on their coats and shuffling up the aisles while one or two last questioners are lingering behind. "Has she finished yet?" one suffering listener asked another as she was departing the auditorium. "Yes," was the answer, "she finished long ago, but just won't stop." Stay in control. End the session yourself by saying, "That's all we have time for today; I want to thank you all for your contributions." Then deliver your conclusion with warmth and confidence. Come forward and mingle with the audience, especially if you have been standing behind a lectern.
If you prepare for questions, take them in stride, treat your audience courteously, and stay in control, the question-and-answer session changes from a time of dread to an enjoyable opportunity. Make it work for you. The back-and-forth nature of question sessions adds to your credibility: You're not just talking to people, you're engaging them. Enjoy it, and your audience will remember you for it.