Pick a topic. You can give a speech on objects, a process, an event, or a concept.
If you are writing your speech for school, a good rule is to choose something you are extremely familiar with. It is a good idea to do at least some research on the topic - the more the better.
Alternatively, you may want to pick a topic you're keenly interested in so you can research it and learn about it.
Remember, informative speeches simply inform people. Don’t choose a topic that will require you to base your speech on your opinion: that's a persuasive speech.
Narrow down your topic. You should be able to thoroughly cover your topic in the time allotted. Pick out a specific purpose for your speech to guide your presentation as well as guide your audience's attention.
Develop your thesis. The thesis is a statement that describes your (narrowed) topic. Ex.:
“I’m going to talk about carburetors” should be "I am going to explain how to take apart a carburetor."
“In this speech, you will learn about zippers” should be "In this speech, you will learn how the zipper was first invented."
Do your research. If there's one rule to writing an informative speech it's this: know your subject. Use reliable sources and take notes as you go.
Consider your audience. It's a good idea to assume they know little about your topic. (Which is why you’re informing them, right?) With this in mind, you may need to give background information and be careful about what shortcuts you take in explaining your topic.
Unless your assignment says otherwise, don’t explain anything that’s a given. Nobody wants to be told what a car or a zipper is.
If, for example, you're giving a speech on carburetors to a group of auto mechanics, you won’t need to give a lot of background information because they already know the topic well.
Outline your speech. Write a list of the information you think should be included and put it in a logical order.
If you're telling people how to do something, your outline might look a bit like the bolded first sentences of the steps in this wikiHow article.
Write an introduction. Your introduction should grab the audience's attention and let them know what direction you’re headed.
Begin with an amusing anecdote or an interesting quote relevant to your topic.
End with your thesis statement.
If it's a long or complicated speech, be sure to lay out what points you intend to cover.
Expand your outline to make the body of the speech. Make it interesting and informative by elaborating on your key points. Have at least three key points for your speech. Organize your speech by chronological order, topic order, or spatial order.
Write a conclusion. The conclusion should quickly summarize the main points of your speech.
Ideally, it should also refer back to the introduction in some way; coming full circle will give your speech a sense of resolution.
Time your speech. If you have been given a time limit, practice out loud and time yourself. Add or cut out material as necessary.
Unless it will be strictly monitored, don't worry if the speech is a little longer than the time limit. When public speaking it's easy to talk too fast. Most people do not slow down.