I'll tell people to read the manual if:
a) It's something so basic that it's obvious they haven't even attempted to look & are obviously using others as their researchers.
b) It's an item of a technical nature (that is in the manual) that either has changed as the vehicles have evolved or is consistently answered incorrectly or with hearsay or speculation.

I also recommend they use the search function if it's a question that has been asked & answered a million times on the forum. eg: what oil should I use; how should I run in my engine; what tyre pressure; what replacement tyre.