Select a topic that you're interested in learning about, or one that you have a bit of expertise in. This will make it easier for you to write the speech, and make it a fun learning process. Select a topic that will be interesting to the majority of your audience. This is the best way to engage your audience. For example: Nanotechnology may be very boring to an audience full of freshman college students, half of whom belong to the cheer squad. On the other hand, this same topic would be intriguing to a class full of science and technology majors.
Open the speech with an attention-grabbing line. For example: If your topic is water pollution, you don't want to start by saying water is essential for all life on Earth. Instead, begin by asking a question: "Does anyone know where that water comes from that pours out of your faucet?" or "What would you do if one day your faucet didn't work and you had to find your own water?" This will immediately grab your audience's attention. This opening line appeals to the survival instinct and seems important enough to engage interest.
Fill the body of your speech with five or six key points, preferably important information, and elaborate on each. Remember to stay on topic, and construct the speech in a manner that flows. Each sentence should have a logical connection to the next, and present information in a smooth flow. Create an outline of the speech body, and under each key point add relevant information. Good key points for a subject such as water pollution would be freshwater shortages, dead zones caused by watershed runoff near home and causes of pollution.
Conclude with a brief synopsis, summarizing your speech, and add flair to the end. You can do this by adding a joke, such as, "So, in closing, forget everything I just told you. Just remember this." Then close with a personal thought or opinion about the subject. This gives the speech a personal touch and leaves the audience in good spirits, comfortable and well-informed.
Practice your speech before you have to stand before your audience. If you have a specific amount of time to meet for your speech, practice slowing your words down to fill the quota or elaborating on key points in your speech body. If it falls outside of your time quota, decrease the amount of elaboration. Practicing your speech aloud in front of a friend, or the mirror, will help significantly. You can perfect your speech before you deliver it.