Organize the information for your paper into a list of topics and subtopics.
Summarize your topics into one main idea. An essay with subtopics such as pet overpopulation, pet health related to mating and pet health after neutering may have a main idea such as "Neutering Pets."
Determine your opinion or stance on your main idea. For an essay on neutering pets, you may take the stance that pets should be neutered.
Write your main idea in a thesis statement sentence that also states your stance on the issue. A thesis statement for a paper on pet neutering may be "Pets should be neutered to improve their health and prevent pet overpopulation."