What are you trying to say?
What's your point?
What's your thesis?

Writers of expository essays often have difficulty trying to define their key ideas, especially when the work is assigned by others, whether teachers or bosses.

In contrast, the goals and purposes of ads are usually simple and well defined: they promise benefits and seek responses.

Ideally, the expository writer ought to have an end purpose constantly in mind: What do you want to say? To whom? What benefit does your audience receive?

Some expository writings (e.g. directions, instructions) have obvious purpose and practical benefit: the reader learns how to do something.

However, many writings do not have such an obvious, immediate, or even a specific benefit, but may furnish the reader with a general knowledge or a better understanding (e.g. of relationships, parts, processes, causes and effects, history) which may provide indirect or future benefits.

Composition textbooks usually suggest that writers try to write their thesis in one declarative sentence: straight, simple, clear and direct, with no rhetorical questions, ambiguities, or figures of speech.

Often, in the outline stage, writers work from a few fragments or a few words jotted down. At some early point, to clarify these vague ideas, it helps to predicate, by specifying exactly, that something is or is not. It helps to change from a "fragment outline" to a "topic sentence" outline.

Useful exercise: Imagine you're going to be interviewed on TV for a 30-second response to answer the question, "What do you want to say?"
Prepare one clear declarative sentence.