This question appears to ask "how to we help OPs ask better questions?" That's simpler when we understand what the VTC reasons mean and why they exist.
As Monica Ciello once pointed out, the nature of Worldbuilding.SE is to fish for answers. Creative people are often looking to forward a story and are experienced writer's block in one way or another. It's not uncommon to have story background to help ask the question, but the question itself must still avoid our common VTC reasons. Unlike non-fiction questions, fiction questions can be asked in an infinite number of ways. The VTC reasons are an effort to control this potentially runaway process.
It is worth noting that we have limitations because we want the site to be valuable to more people than just the OP. Others should be capable of benefiting from the effort to ask and answer the question.
As I currently understand them...
Primarily Opinion-Based (VTC:POB)
- Questions are often specific, but lack direction.
- Question usually becomes on-topic by adding background or definitions.
- Answers are usually 1-4 paragraphs, but they are frequently disparate (all over the map).
- No one answer can be any better than another.
- Reason we care is that questions without an obviously relevant answer are less to others.
Off-topic example: "How can my armored soldier survive a javelin attack?"
On-topic example: "How can my armored soldier survive a javelin attack such that he can walk off the battlefield even if the armor is damaged?"
Too Broad (VTC:TB)
- Question may be ambiguous, reflecting a lack of research on the OP's part.
- Question may be ambiguous, reflecting a lack of understanding about the question.
- Question may be ambiguous, reflecting a desire for far more information than the site is prepared to provide.
- Question may ask too many questions.
- Question is made on-topic by reframing it as a single, unambiguous question.
- Answers often require a "book" sized response.
- Answers often require only seconds on Google to obtain scoping information.
- Reason we care is that future readers are unlikely to find value in very long answers.
Off-topic example: "What kind of spaceship can fly near a black hole?"
On-topic example: "Does science know of, or theorize, a meterial that could be used to build the structure of a spaceship that could fly near a black hole?"
Too Story Based (VTC:TSB)
- Question does not ask about the rules of a fictional world that could be used to write many stories.
- Question does ask about a plot device, behavior, action, or event that is meant to advance a specific story and is often independent of the rules of the fictional world.
- Question is usually made on-topic by rephrasing to remove story elements.
- Answers are often "this is what would happen next..."
- Answers are frequently disparate (all over the map, by their nature TSB questions are POB questions).
- Reason we care is that story-specific questions often interpreted as usless to other people.
Off-topic example: "How should my thief, John, rob his medieval feudal lord of his best ring?"
On-topic example: "How could an affluent medieval person protect small valuables from theft?"