What the FAQ says ...
Okay, so let's imagine I'm completely new to the site, and I have a question closed. However, I think my question is perfectly valid, or I'm totally confused about why that even happened. Nobody cared to write a comment about why it was closed.
I start thinking about it, and I'll try to read the FAQ. Here's what I read:
Questions that are not a good fit for this site may be voted closed by experienced community members. Closed questions cannot be answered, but are eligible for improvement (and eventual re-opening) through editing, voting, and commenting.
Users with 3000 reputation can cast up to 50 close votes per day. When a question reaches 5 close votes, it is marked as closed, and will no longer accept answers. Closed questions may be opened by casting reopen votes in the same manner. However, you may only vote to close or reopen a question once.
To a new member of the site, this may seem
overly detailed: The reader might ask, "What do I care if members with reputation over 3k can cast 50 close votes a day?".
missing details: The FAQ says, "may be voted closed by experienced community members" and "when a question reaches 5 close votes". This is not always true. In some cases, the question can be closed by a moderator only. From my experience, some moderators are more likely to intervene, while others only step in if there are already some community votes. As the FAQ doesn't even mention that at all, it's confusing.
missing guidelines: My question has been closed. Now what? In some cases, the moderator who closed (or one of the five >3k users) might not have even left a comment. The message points to the FAQ, but the FAQ says only little about how one would go and get the question reopened.
Should the user edit? What should they edit? "Voting"? How? "Commenting"? Should the user start pinging every user who voted to close?
Obviously, there are too many open questions here.
the other one was closed because "this question will likely solicit opinion, debate, arguments, polling, or extended discussion." So I rephrased it.
They didn't know they had to edit their old question and what to do exactly to have it reopened. The procedure of having a question reopened is clearly insufficiently addressed in the Stack Exchange network's FAQs.
This part of the FAQ should include more information. Here are a few ideas I came up with initially, but go ahead and suggest changes if you like!
As @YannisRizos mentions, it would also make perfect sense to create new page similar to the "How to Ask" and "How to Answer" pages that the "closed" message would then link to, instead of just extending the FAQ for this very special case.
Either way, this is what I think it should look like:
What can I do to get my question reopened?
Carefully read the message below your question. The text should explain why it was closed and point you to the FAQ. In order to have it reopened, you will have to edit your question to meet the standards outlined there. Take into account any constructive comments you received, and read the How to Ask guide.
Once you edited the question accordingly, you may use the "flag" link to inform a moderator about your changes.
They will judge if the question is worth reopening. Similarly, users with 3000 reputation can cast a "reopen" vote, which behave the same as close votes.
You can also visit Meta to post a "reopen request".
What should I not do?
Do not post the question again. Chances are it will be closed too, and also possibly deleted. You always need to fix your closed question first.