There is plenty advice around for "how to ask" (really, it's the same if you know the person or not). It all boils down to a Calvinistic "show you're worthy" kind of exercise.

But what about advice for giving help to someone?

There's plenty of ways that giving someone help can go horribly wrong, and I think that it's not uncommon for people to be blindsided by such a request.

A pretty incredible answer to your question comes from a perhaps wholly unexpected source: Hunter S. Thompson, in a letter responding to a friend's request for life advice:

https://fs.blog/hunter-s-thompson-to-hume-logan/