I don't understand how listing in threes (sometimes called the "power if three") help when writing descriptions eg. guttering, chocking, drowning. How are these three words useful?
There's nothing special about the number three. I've never heard "power of three" except as an expression in mathematics. In writing descriptions you could use two, four, or in theory any number of words.
I think the example you give (guttering, choking, drowning) is from a poem that describes a person dying of poison gas. Each of these three words gives you a slightly different picture, to help you see and understand the experience in your mind.
This is what happens in good writing: Each word adds something. Of course, there's a lot of bad writing around, and sometimes words are added for no reason.
best wishes
edward
Actually, there is a rhetorical principle that says that listing things in threes can have a powerful effect on the audience. It seems that the human brain can process three pieces of information at a time, and so saying basically the same thing three times is highly effective.
The current British government came to power saying that the three most important things were: Education, education, education. If you imagine a politician making that speech, but saying "Education" only twice, or four times, it loses a great deal of impact.