Keep in mind that an expository essay is one of the simpler assignments you can receive, if you follow the correct steps in writing it. Basically, a process or description of something is pretty black and white, and it's important to keep that in mind while writing to keep your style as expository as possible.
First, choose the subject for your essay. A process or the steps to complete a task is always a great theme to choose, because methods are usually unvaried and the reader gets what they came for: to learn about something they didn't know. Once you have your topic in mind, whether it's the steps to building a wooden bird feeder or learning how to sew, set aside a fair amount of time to research. The Internet is the definitive method of choice for most research needs today, but don't discount books, magazines and trade journals that can be found at your college library. Sometimes, these have insider information that you might not find online.
Once you have your topic and the necessary research about that topic completed, it's time to structure your essay. Sometimes, a simple a step by step guideline will do the trick, but other times more explanation is necessary.
Start with an outline that defines your lead at the top, your how-to statement or exactly what you're examining. Next, draw up a basic thesis statement that supports your main theme. Make sure that you can accomplish what you're setting out to do in that thesis statement with the research and data you have gathered.
Next, plot out the body of your essay. If you're writing a simple step-by-step guide for a daily life process, your body will consist of several small paragraphs that compile the steps. If you're examining an issue or filling your reader in on an issue of importance, your body will be fewer, larger paragraphs. It's a good idea to think in the step-by-step mindset, even if you're explaining something that isn't a simple process. This will help you avoid inserting your opinion or feeling statements into your body, which are the antithesis of a good expository essay. Remember, it's all about the facts; writing that a town's citizen was murdered should talk about the who, what, when, why and how he was murdered, not how everyone felt at losing their beloved neighbor Charlie or how it sickens you to think about crime occurring this close to home. Leave these descriptors for other essays. Also remember to include diagrams, photos, charts or any other tools that may help your reader understand the subject you are explaining.
After you've plotted out the meat of your essay, it's now time to wrap it up. First, sum up what you've just shared, and make sure you've achieved your goals. It's a good idea to offer an optional further call to action for your reader; if you wrote about how to register to vote, provide your reader with a few resources that may be of further assistance. Finally, if possible, ask someone you know that has little or no knowledge on your subject to read your essay and explain back what you were trying to convey. If they can, you have written a successful expository essay.