Ask HN: How do you find domain specific knowledge?

Let's say you're doing your job and you realise you need some sort of domain specific knowledge to proceed (or to do your job better). I'm talking about domain specific knowledge, perhaps the kind of knowledge someone else in your company has needed before. How do you go about to finding it?

I've found this to be one of the main challenges at the startup I currently work for. As someone in charge of making a change, I wanted to gather some external use-cases before jumping into a solution.

Would love to hear your thoughts!

Cheers!