Should I be using PM or forum to ask questions?

I've recently sent a message to a mod (no names needed, this isn't a complaint) asking about upload tips and I was even expecting a cold response but I got none, I guess he was probably just too busy, had many pm's already or felt unnecessary to answer since Danbooru itself would answer me anyways where to ask about this when my posts get deleted. So my point is: is it using private messages to ask about the site itself and tips on how being a better user in general encouraged or is it better to post these questions on forum or maybe the Discord server? I've done some research but found close to nothing on how to use private message, that's why I'm asking it here. Thanks in advance.

The forum has many threads for tagging and whatnot, but no single one for general advice. You could still make a thread asking questions, though. DMing for such things probably isn't ideal. Not all mods are as active as others.

The Discord will get you the most and most diverse set of responses, as well as being faster than the forum or DMs. 'Tis the nature of live chatting.