Diction is the process of word selection.
Writing well involves choosing words which play nicely with one another, then killing off as many as possible; leaving only as many as necessary to clearly articulate your point.
“I think I might like to apply for that job. The pay is pretty good, and Sarah said she could probably help me to do up a resume if I wanted a hand.”
Is far easier to read when we apply this logic;
“I’m considering applying for that job. The pay is good, and Sarah said she’d help with my resume.”
When writing, we add words that we use in speech, despite them adding no value to our sentences in writing. We use words like “pretty”, “very” and “probably” to buy time; forcing them to fill gaps in our trains of thought, or jamming them into awkward silences.
These don’t belong in our writing. Consistently considering diction helps break the habit.
Word selection is also what makes writing funny, witty, or clever.
Humour lives in surprise. It’s why comedians spend their lives honing timing, and why bad jokes get big laughs at funerals; things are funniest, and therefore most interesting when they are least expected.
When introducing a character, never write;
“Joy is a little bit strange sometimes.”
When you could write;
“Joy adores the smell of petrol.”
Why would you write something vague and boring when you could write something specific and intriguing?
Make a choice.