You need a unique mix of ingredients to qualify the exam. In the recently concluded competitive examinations, I met a candidate who wrote a three- to four-line outline and gave a few headings in essay yet he managed to clear CE-2014 exam with 46 marks. So, yeah, no fix set of axioms that will get you through.

As a rule of thumb, you should keep the following points in mind while attempting a CSS essay:

1) An outline which tells WHAT, WHY/CAUSES, HOW/EFFECTS, OTHER SIDE OF THE ARGUMENT & WAY FORWARD for the essay topic that you have chosen.

2) Go for an argumentative essay. Well, now, almost all essays are argumentative in nature.

3) Always present both sides of the argument. For instance, one of the topics in CE-15 was: "Labour-saving devices are more troublesome than they are worth." You should tell about the pros as well as the cons.

4) Include a clear-cut thesis statement in your introductory paragraph. It should incorporate the other side of the coin as well but it should delineate your position clearly mentioning two to three arguments. E.g., for 'I disapprove what you say, but I defend to death your right to say' essay, the following thesis statement is pretty apt:

Although tolerance cannot be exhibited at all times, say, hate speech, by and large, it is to be exercised because it leads to social stability and birth of new ideas.

5) 1500-1600 is more than enough to qualify the essay exam. But if you want to score 60+, write at least 2000+ words.

6) Logical Flow. Coherence. Linking (transitory words b/w paragraphs such as On the other hand, Additionally, Similarly, Likewise, In stark comparison to...). All these three guys are very important. Get hold of them.