We started by saying that sentences express ideas. We can now add that:
The sentence is the smallest literary unit that expresses style.
Single words do not express style; it is only when we start stringing words together that our voice is heard.
To focus on improving your sentences is to start developing your own identifiable way with words. Once you start to write regularly, you'll find that your writing starts to match the cadence of your thoughts, which usually matches the cadence of your speech as well. And once you gain some confidence getting your thoughts out on paper, you can begin tinkering with subtle changes to how you deliver your ideas. As always, context determines the choices you make, and your sensitivity to context improves over time.
For example, in the section on syllables I wrote a paragraph where every sentence had roughly the same feel. It was awkward. The words did not flow well, partly because the sentences were so similarly structured. Stylistically, this seemed a poor approach.
Instead, I suggested varying the length of sentences and finding words that fit well together sonically. Of course, this is all a matter of taste, much like music or art. But writing is an artistic pursuit -- essays included -- and so is subject to the whims of the reader as much as music is subject to listener.
Though we read silently, most often, it is the sonic quality of words that guides our writing. We imagine the words spoken, or we hear the words in our head as we write. And just as our favourite musical performances are likely those that sound effortless or natural, so too is our favourite writing. I can tell you that the blues turnaround is on the fifth of the root chord, but I can't tell you why the turnaround gives a sense of "closure". Similarly, I can't tell you why certain words in a certain order sound pleasant in the ear. This is simply something that you learn by listening to words in the world.
I say all of this to emphasise that our pursuit is quite decidedly subjective. There's no algorithmic way to make anyone a better writer; some go so far to say that good writing cannot be taught. Perhaps there's some sense to that, but we can rest assured that any skill can be improved through guided practice.
Now, when you start crafting sentences, you'll want to focus on one thing at a time. After some practice, that thing will become natural, and you won't need to focus on it anymore. This resembles the way you learn a sport. For example, I may tell you to model your tennis backhand on the way you throw a Frisbee. Then, we practise that motion over and over until you start striking the ball on the sweet spot and directing it roughly where you want it. Then, we may start considering how to impart spin on the ball by moving your hand as though you're offering someone a chocolate -- but now we're no longer thinking about Frisbee! That's done and dusted and we're on to the next thing.
While crafting sentences, start with considering active versus passive voice. At first you'll likely have to think about subject choice and the like, but after a while, you'll find yourself simply writing active sentences effortlessly. Now, on to the next thing -- maybe cadence or metaphor.
Once you've got these mechanics down cold, time to start thinking about the experience of the words. That is, think about how they work together -- how they flow. Does this sound good in the ear? If so, move on. If not, reconsider your choices, notice what you improve, and work to do the same but better next time.
Before you know it, you'll be jotting down thousand word essays in the blink of a morning tea.
The next reading is a second from George Orwell, and in it you'll find him making heaps of comparisons. As you read it, consider how the scene he describes in his essay might be a metaphor, and pay attention to how he moves from one idea to the next. Try to get a sense of how his prose flows.