I'd love to figure this out. I've written more about them than most people at this point, and my goal has always been to help people learn what they can and cannot do - but distilling that down to a concise set of lessons continues to defeat me.
The only way to really get to grips with them is to use them, a lot. You need to try things that fail, and other things that work, and build up an intuition about their strengths and weaknesses.
The problem with intuition is it's really hard to download that into someone else's head.
I share a ton of chat conversations to show how I use them - https://simonwillison.net/tags/tools/ and https://simonwillison.net/tags/ai-assisted-programming/ have a bunch of links to my exported Claude transcripts.