[header] How to write an expository essay on an animal [title] Think of a topic. [step] The first step to writing a solid expository essay is to settle on a topic. As you already have animals as an overarching theme you'll need to specify further. 
What animal are you writing about? [substeps] An expository essay is an essay that provides the reader information about a particular topic. To write an expository essay on an animal, you'll have to choose an animal and provide a variety of information on that animal.