How can I determine if the question I'm about to ask is a good and valid one? Are there guidelines I need to follow or a checklist I can go through?
Also what's the best way to make sure that I'm not accidentally asking a duplicate question?
If the answer is yes to most or all of the above, the question is good.
Search. Look at the questions that come up after you finish typing up the title of your question.
When searching, use the relevant tags in
You can search for the key terms, and when you start asking, it will show you possible duplicates - check them to make sure your question has not been asked.
And if it is a duplicate, then someone will pick it up, and point you to the duplicate version. As long as you have taken care, this should not be considered a criticism.