Curse of knowledge applies here unfortunately, in that it was so long ago I can’t be a reliable source on how to learn now. I recall being recommended “never split the difference” at some point and reading it and finding it useful (again, so long ago I can’t remember what’s actually in the book now).

I’d also try to hunt down a peer or someone just slightly more senior than you who you suspect is better at this than you and ask them for advice. Consider treating it a little bit like a behavioural job interview though. Questions like “so for your last promotion cycle, when did you start the conversation with your boss? What did you present to them? What format/medium? How often? What was the result? What did you expect? Did you have a Plan B? How often are you exploring other options just in case?” not so much “what would you do in this situation?”. If they’re successful you’ve more to learn from what is actually working from them rather than their hypothetical ideal.