The first step is to check with the individual education PhD programs to see what kind of writing sample they require. Some may have specific guidelines, such as length or topic. Once you know the requirements, you can begin brainstorming ideas for your writing sample. If you're having trouble coming up with an idea, try thinking about a time when you had to solve a problem in your field of study. Alternatively, you could write about an issue that you're passionate about and explain how your research would contribute to solving that problem. Whatever topic you choose, make sure it showcase your skills and knowledge in the field of education. With a strong writing sample, for example, you'll be on your way to impressing the admissions committee and getting into the education PhD program of your choice.