There seems to be a distinct overlap between using down-votes vs. using the flag reason "Unclear what you are asking".
This question does not show any research effort, it is unclear or not useful
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 How to Ask page for help clarifying this question.
Other than the "not useful" bit, they say pretty much the same thing. How do we select between one or the other? Are there any canonical guidelines?