This post is a summary of the YouTube video at https://youtu.be/FHEAmAyMdG0 , which focusses on prose.
1 SHOW, DON’T TELL It mostly applies to emotions and senses. Words like “angr(il)y”, “sad(ly)”, etc. are “telling” words. How is he angry, what does he do as he stands up that makes it obvious he is angry? Imagine that the character was in a movie without narration. You have to convey emotion by what he looks like and how he acts, rather than saying something directly.
2 USE ACTIVE VOICE OVER PASSIVE Words ending in -ing are passive, and should often be made active. Passive voice sounds weaker. “He was standing at the front of the room” (passive) becomes “He stood at the front of the room” (active). Passive voice can be good if the character himself is passive.
3 TO BE OR NOT TO BE “To be” words weaken sentences.
4 VERBS ARE BETTER THAN ADVERBS A strong descriptive verb is better than a more generic verb paired with an adverb. So don’t say “She walked lazily across the room”, say “She ambled across the room”
5 NO THINKING Avoid “realising/remembering/knowing” etc.. don’t have a character realise something. Present the facts to the reader so that they can realise it.
6 DOUBLES ARE TROUBLE Using the same word multiple times in a passage is a sign of lazy writing.
7 CHOOSE YOUR WORD WISELY Be aware of every word you use, and justify its use to yourself.