Be polite. The person who gets your letter will seldom be the one who wronged you. And is unlikely to pass it on to the desired recipient if you are insulting and raging.
Make plain how you’ve been inconvenienced, then propose what’ll seem to your correspondent a reasonable and proportionate redress that’s within their power to make. And be sure to phrase your redress as a request instead of a demand.
Always remember that your job, writing to a friend, is to entertain. That can mean revelling in the odd pratfall. So, don’t just write about the mundane and pleasant things, try to give them the whole picture and make them feel something.
The love letter is about attention. You’re being your best self – most alive to the world, most engaged with the other – so that the attention you’re paying to them becomes a fantastic compliment.
Some say that what makes a relationship work is not how you feel about the other person, but how they make you feel about yourself. Be sure to include that in your letter and to show that you are intoxicated with them.
Forget what you know and want. Everything, from the shape of your argument to the choice of vocabulary, should be governed by your audience’s receptivity.
The key principle of persuasive writing is customer service. Ask what they do and don’t know about the subject, and what they need to. Ask what they are likely to find funny. What are the shared references that will bring them on board? Where do you need to pitch your language? How much attention are they likely to be paying?
Plain English (the simplest word that does the job; straightforward sentences; nice active verbs etc) is far from the only style you should have at your command. But the plainer the language, the easier the reader finds it and the more likely they’ll take in your message.
Language changes according to usage and there’s no referee or court of appeal. With some nonstandard usages increasing the expressive range of the language and its precision.
All that being said, many readers place a premium on “correctness”, or the idea of it. Besides, it implies intellectual authority, and it’s the best way to communicate in formal situations.
English audiences prefer short sentences and a subject-verb-object order.
Avoid a huge series of modifying clauses and parenthesis before you reach the subject of the sentence, else the reader’s brain will be working harder to make sense of the sentence. Meanwhile, you’re distracting it by cramming ever more material into its working memory.
Most of what gets described as “good writing” is so described because – one way or another – it sounds right. It flows and slows when it should, the stresses fall naturally on the words that the writer wants to emphasize and the reader doesn’t stumble over unintended internal rhymes or clumsy repetitions.
Reading something aloud is a good way of stress-testing it: you’ll notice the rhythm more. Also, you’ll notice very abruptly if your sentences are too long or confusing.