This is what I do based on what I've seen other more experienced users do, including yourself :)
If a question is vague based on how it's written, I'll usually edit it, with a comment such as:
I've edited your question in an attempt to clarify a few details regarding [type here] — please edit further to extenuate any details and further clarify the problem.
If a question is vague because it's missing essential details, I'll usually write a comment myself from scratch explaining what's missing then vote to close as unclear.
However, there are some questions that need a general assistance in being written. If I think a link to the How to Ask page would be useful, I'll comment the following, then VTC:
Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the [ask] page for help clarifying this question.
This is usually prepended automatically with 'Welcome to Ask Different!' as the user is usually new in this case. ARC is a wonderful thing :) If anyone's interested, here's my comments that I use for reviewing posts on Stack Exchange.
This isn't really a case like the others above and doesn't happen often, but something that can make a question unclear: a title and body that doesn't match. If the body is longer than the title, I usually edit the title to match the body, adding the following comment when I do so:
Your title and body seemed contradictory, showing two different problems. I've edited the title to fit the body, but feel free to re-edit and clarify the situation.
I am more reluctant to change a body to match a title.
In summation, I believe the above works generally well and although some data would be helpful here, it seems that…
- in the first case the question usually gets a suitable answer, either from myself or from someone else,
- in the second case the OP either edits before the question gets closed and so avoids closure or edits after closure and is reopened either by someone seeing the question or from the Reopen queue,
- in the third case the user either edits their question or never comes back and the question gets auto deleted, and
- in the fourth case, nothing else really happens and people carry on as if the title had been written originally.
In rare cases, I'll sometimes do one of the above and also answer myself based on educated guesses. This is either approved by the OP and I edit the original question based on the information that I've presumed, or is declined by the OP and lets them see exactly how their question could be perceived, which is generally different to how they believe they've portrayed their problem and is the reason for the lack of clarity.