in my opinion headings are more than necessary...important thing is how to attempt ur question?here u make a difference,,,first read the question thrice, underline the main asked aspects of question,,,now think what u will discuss in this question, make ur points in rough work which will be ur headings, in case of islamiat write the hints of ahadith and ayat u will mention in the answer...this practice will take u 3-4 minutes but u will write a comprehensive and managed and focussed answer,,all the best