Many people prepare for speeches by writing out the full text of their remarks and rehearsing to get the words exactly right. This often means you end up delivering a speech exactly as you wrote it, even if the audience isn't responsive. Speaking is different than writing. You need to connect with your listeners. Prepare for your next speaking engagement by jotting down a list of four or five brief, key points and a concluding paragraph. Then arrive early enough to talk with people before your speech. This allows you to grasp the mood of the audience and tailor your points to its state of mind.
Source: "Managing Yourself: Extreme Productivity" by Robert C. Pozen