1. Some writers complicate their prose to impress. They wrongly think that the more complex the writing the deeper the thinking. Fact is the less clear the writing often means we don't really know what we're talking about.
2. A writer is too self-conscious about their writing so that they over think as they compose. They are afraid to make even the slightest grammar mistake.
3. Some writers especially those new to a subject freeze up as they are trying to think and write. They are intimated by the material and consequently the prose worsens as we seek to master a new idea.
4. Writers cannot predict what bits of their writing will appear unclear to a reader or even what makes it unclear. They point out that our writing always appears clearer to us because we don't read out what we've written, we read in what we think.
Williams and Colomb argue that the most important skill to master in order to write clearly is how to objectively analyze your writing that is "on the page".
One other point of advice the first lesson raises is one I have found so true and can be captured in a saying I've been repeating since reading it during my doctoral days:
"Good writing is the result of many revisions".As Williams and Colomb put it, "most experienced writers get something down on paper or up on a screen as fast as they can. Then they revise that first draft into something clearer" (8).