Considering Paragraph Structure

Oftentimes, writers break to a new paragraph without a lot of thought. When you have a new idea, start a new paragraph is the guideline under which most of us operate. Yet, when we think about it from the reader's perspective, when a paragraph does not contain a complete thought or when a new paragraph makes a giant leap to a new subject without warning, our heads are left spinning!

So, as writers, there are a couple of things we can do to keep our readers from getting lost or frustrated. Using the mnemonic device MEAL, we can remember what should be in most paragraphs...

M - ain idea: This is your topic sentence; it sets up your reader to know what the paragraph is about

E - vidence: Of course, most main ideas need a little justification, so your evidence portion is a couple of sentences that back up your main idea.

A - nalysis: You're writing about this topic, because you have something to say about it, so what is your take on the main idea and the evidence you've cited?

L - ink or Last thought: This is a sentence or two where you conclude your thoughts and/or provide a linking sentence to the next paragraph.

Let's look at an example from an NIH award abstract:

Main  Evidence  Analysis  Link/Last thought

Excessive anxiety and fear leads to anxiety disorders, which impact many aspects of life, from the interpersonal to professional spheres. Although each anxiety disorder has different symptoms, they all share a core feature: mal-adaptive expression of high levels of anxiety. In our study, we will study how the brain suppresses anxiety. Prior studies showed the amygdala is largely responsible for generating high anxiety and fear, while the ventral medial prefrontal cortex (vmPFC) decreases these behaviors, possibly by inhibiting amygdala output. Indeed, in humans higher vmPFC activation correlates with lower amygdala activation and decreased anxiety. These data suggest the vmPFC-amygdala pathway may decrease anxiety and fear, but they rely on correlative measures, and can't directly test this hypothesis. We used optogenetics to directly test if the vmPFC-amygdala projection suppresses anxiety and fear. 

Remarkably, optogenetic activation of the vmPFC-amygdala pathway robustly inhibits innate anxiety and learned fear, while inhibition of this pathway increases anxiety.... 

As with any writing rule, there are exceptions and easily-readable paragraphs that leave out one component or another. Yet, when you pull all of the paragraphs together in a section, they should include all of the MEAL components pretty regularly.

In terms of paragraph organization, Otto Yang, in his book, Guide to Effective Grant Writing: How to Write a Successful NIH Grant Application, offers a technique to better construct and organize your paragraphs.  For one section, take the first line of every paragraph and put them together to see if those lead sentences alone give you an understanding of the piece.  This is important especially for grant-writing where reviewers often skim the numerous proposals they review. Giving your reviewers clear sign posts at the start of a paragraph will be much appreciated.

Although these techniques are helpful when you're writing, often they're more useful to apply when you are re-reading and revising.  You've already gotten your thoughts down and they seem to flow, but perhaps you'll realize in making revisions that your reader will have to read half-way through many of your paragraphs before they understand your main point.  In this case, it may serve you and your reader well to apply some paragraph revisions.

Resources:
Paragraphing with the MEAL Plan - Capella University
Paragraphs - University of North Carolina Chapel Hill Writing Center