Everything in the faq and faq-proposed tags is important and pretty much up-to-date (even if they haven't been updated in a long time).1 They are generally extremely comprehensive. In particular, these two posts are especially informative about the Meta community itself.
As for filing a bug or feature-request, make sure that in addition to searching, you scan the top voted bugs and requests. status-bydesign and status-declined are also good places where newcomers often don't realize topics have been discussed before. Sometimes they're old, but phrased a bit differently.
Before posting a new question, make sure you search meta, trying different keywords to make sure it hasn't been posted before.
If you feel something is a good idea and you've voted it up, but it's still got a low number of votes, and you feel strongly about it, you can always mention it in chat and see what the rest of the community thinks. You can also edit for grammar (some of the old posts do need a bit of a cleanup) and bump the post while you're doing that. Posting duplicates isn't a good idea, because it spreads out valuable votes across multiple questions, so the Team might not see those.
As for posts being outdated, any high voted bug or feature-request which has not had been marked status-completed or status-bydesign is probably being actively monitored by both the Team and the Meta community, so inactivity might just mean there hasn't been any real change, not that they've fallen by the wayside. [status-declined] is a bit unusual. Usually, the reasoning behind a decision will still stand, but sometimes things have changed. In that case, the usual Meta procedure is to post a new answer explaining why things have changed.
My post has gone slightly beyond the bounds of your post, but I think this is a pretty good beginner's post to using Meta and answers your title quite well (but I would be biased anyway).
The only thing I can think of is that favorite tags
are probably still referred to as interesting tags
, but that will get fixed sooner or later.