The FAQ page for Skeptics.stackexchange.com gives some brief guidance to what questions are on-topic and off-topic:
Skeptics - Stack Exchange is for skeptics, rationalists, free thinkers, or anyone who questions pseudoscience. Skeptics is about applying skepticism — it's for researching the evidence behind the claims you hear or read. It is not for philosophical discussions about skepticism itself.
If you have a question about the accuracy of public claims made in the media or elsewhere, if you're interested in the evidence behind what you hear or read, then you are in the right place.
If your question is not about a particular claim, or if it is about research-level science, the following sites may be better suited for your needs: [...]
This is an good summary, and continues to be used an overarching principle. However, the boundaries of the scope of Skeptics.SE continues to be explored and debated.
Based on discussions and precedents, what topics are in and out of scope if Skeptics.SE?
There is a related question about what makes a good question. This question, on the other hand, is focused on the general topic of the question as opposed to how it is asked.