Comparison and cadence
Here we'll talk briefly about two things: comparison, and cadence. These "devices", as we'll call them, help keep the reader engaged in your writing. Under the heading "comparison", we'll look at similes and metaphors. Under the heading "cadence", we'll look at alliteration and syllables.
To put it simply, a simile is a comparison that uses "like" or "as". If we say that his suit fits him as a stall fits a horse, that's a simile. (It's also borrowed from Raymond Chandler's The Big Sleep. Chandler was a master of comparisons.)
We compare things this way in order to introduce perspective, or scale in a scene. (Note that non-fiction writing contains scenes just as much as fiction writing.) We often use comparisons in place of adjectives.
In the case above, Chandler could have said that "his suit was too big for him", but that's a bit of a dead description. Instead, Chandler enlivens the description through comparison: not only is the suit too big, it creates the sense of a container rather than a vestment. We can imagine the character walking awkwardly, trying to slough around this overbearing thing with him. We can imagine the character fighting against the suit, wanting to get free of it. And we imagine these things by virtue of the simple comparison to a horse stall.
Similes conjure pictures worth thousands of words.
Fair warning: don't let your simile be more memorable than your point. A good friend once described what was perhaps the most vivid simile he had heard: "it looked like someone had thrown a hand grenade in a long drop". Unfortunately, that stunning visual dislodged the speaker's main point, which, to this day, he can't remember.
To put it simply, a metaphor is a comparison that does not use "like" or "as". In this case, rather than say that one thing resembles another, we say that one thing is the same as another. Notice again we're dealing with this recurring consideration of "sameness".
Burger King might be a chain, but it's certainly not forged of steel. Here, "chain" is a metaphor. All Burger Kings share certain properties, and as such, are "linked", we may say, though there is no physical path from one shop to the next.
Similarly we trace through chains of reasons, which are clearly not twisted metal rings. The people in a chain of command are free to move about without interfering with an adjacent link. And so on. The point of the metaphor is to suggest a connection between two ideas, and that connection should elucidate a possibly misunderstood aspect of the one idea using a presumably better understood aspect of the other idea. A golden opportunity is a valuable opportunity, but comparison to gold suggests a (social) preciousness that isn't necessarily part of the word "valuable". In the interests of concision, a "golden" opportunity would be preferred to "precious, valuable" one.
Metaphors elucidate relationships efficiently.
When you say that one thing is another thing -- though it clearly isn't the same -- you also use metaphor. That old shed isn't but a pile of sticks, we might say when we notice haphazard or poor construction or a severe lack of structural maintenance. Obviously the shed is a shed and not a pile of sticks. The point is to say that the shed doesn't look particularly sturdy, but to say so in a colourful way.
In both cases of simile and metaphor, we could have used simple adjectives instead of comparisons, but as we said at the start, part of comparison's role is to engage reader interest.
When a series of words start with the same sounds, that's alliteration. (The repeated "s" sound in the previous sentence counts as alliteration.) You might think there's absolutely no point in introducing alliteration, and sure, you can easily write without such sonic tricks. But insofar as we're interested in attracting and retaining readers' attention, a well-placed alliterative flourish can wake up a sleepy text. (That's a metaphor!)
Alliterative phrases also tend to be more memorable, and if you're trying to be more memorable, then by all means use whatever you can to achieve that end. For example, you'll surely have an easier time remembering the name of "Big Bill's Broom Shop" over "The Cheltenham Broom Emporium". The one rolls off the tongue (another metaphor!), and sometimes that's precisely the kind of impact you want to have.
Sentence lengths should vary. Varying sentence length improves readability. Readable text is better for making points. Adjust sentence lengths accordingly.
How horrible is that first paragraph? All the sentences have the same structure and are roughly the same length. I've read entire essays written like this, and trust me, the agony is real. To begin with, you need to vary sentence and word lengths.
Stylistically, I tend to write a few complex sentences then end with a simple one. That first paragraph again: "Try to vary the length of your sentences, as this improves readability and improves the impact of the points you make. Consider context and adjust accordingly."
After you've worked on this aspect of your style, you can introduce sounds and syllables that go together neatly. Here's my favourite example of cadence from Warren Zevon's song "Werewolves of London":
"Little old lady got mutilated late last night / Werewolves of London again!"
OK, so the image is a tad rough, but those syllables are simply made for one another. The repetition of the syllable "LAY", combined with the alliteration, makes this, to me, one of the most memorable lines in pop music. The next activity asks you to consider lines that stand out in songs you love. Keep these thoughts in mind as you proceed.