You are usually asked to give a presentation because of your expertise on a particular topic. Your goal, then, as a speaker is to help your audience gain a level of understanding about your subject matter.

While standing up in front of your audience and merely talking is one option, using support materials to drive home your key points as you speak is the more effective choice. The most successful speakers also use a mix of different materials, including:

Facts and Statistics
Facts are observations or events that are known to be true. Statistics are numerical data that have been collected and measured; they are only factual if they have been gathered fairly. Both can be effectively used to emphasize or demonstrate a point.

Case Studies
While pure facts and statistics compiled from studies can be convincing, stories of real people in real situations are often the most compelling. Case studies that pertain to your subject matter make the facts and statistics come alive for your audience.

Personal Anecdotes
In the same way that case studies bring facts and statistics to life, anecdotes about the speaker's experience with the topic help humanize the presenter. Getting the audience "on your side" is one of the speaker's biggest challenges; personal stories can be an important tool.

Analogies
Drawing parallels between things that are known to the audience and your topic can be effective, especially if your subject matter is well outside the scope of their everyday lives. Analogies are also useful in simplifying very complex information.