I realize that downvoting the question because it is unclear, or closing the question because it is to vague is not only an option but Standard Operating Procedure... but does that really help people looking for an answer?
Remember that in essence, this is the only kind of feedback we've got. It's often not as bad as you put it. Here on Super User, we don't even have that many people who actively moderate and cast Not a real question close votes. In fact, people don't even downvote as much as the system would allow them to. Since downvotes on questions are free (i.e. don't reduce your reputation), it's even encouraged to downvote more (emphasis mine).:
We feel that the world is awash in questions, but not answers. Answers are the real unit of work in any Q&A system. Therefore, the only logical thing to do is to maximize the happiness and enjoyment of answerers. If this means aggressively downvoting or closing unworthy and uninteresting questions, so be it. Without a community of people willing to answer questions, it really doesn’t matter if there are questions at all, does it?
Of course it's not exactly helpful for people just looking for an answer. But that is not what the site is about. We don't want to encourage people posting vague questions with no intention to do a little research themselves or even look after their posts. If these questions get downvoted and closed, so be it. We also don't want to feed help vampires.
There are enough users who take downvotes/closed questions as an opportunity to learn how to use the site and learn how to help themselves. I honestly have to say, I don't feel sorry for those who don't. Vague questions are a waste of everyone's time – asking for clarification, editing posts, voting, closing, reopening, all the fuss that comes with that.
If you get a few questions closed, then you should really start thinking about how do better approach your problem solving strategy. Often – and simply just because they don't want to be downvoted or have their questions closed again – people actually start helping themselves. And once we have enough information to work with, this is where this community can shine: by providing awesome answers.
Not only how do you get people to pay attention to "How to Ask"... how do we get people to help us help them?
The same like we've always done. People need to harden up and cast downvotes if they think a question is missing information or the OP has not tried to explain clearly. Of course, you should leave a comment asking for clarification. Many first-time askers don't know where to look and they really shouldn't get comments like:
This question is too vague.
But rather:
-1, this question is too vague. What is your operating system? What did you do when you fooed the bar? Is your yak turned on? Please [edit] your question to include this and that, otherwise we can't really help you.
This is nudging them in the right direction but still giving them an incentive to fix their question.