What is the secret to source questions

The secret to source questions is to keep it simple - extra knowledge is useful, but it is important not lose sight of the source at hand or the question. When you look at a source one must identify the NOP (Nature, Origin, Purpose).Nature - what is the source i.e. pamphlet, painting, article,Origin - who produced the source, in what context , Purpose - who is it for/ or was it meant to be public? why was it produced?
You must then relate this to the question