When writing essays, you must comprehend the question before you actually put pen to paper. Therefore, you would analyse the key words in the question.
For example, if the question was .... Analyse Stalin's positive contributions to Soviet Society.
Then, you'd underline Analyse and Positive.
Furthermore, teachers are constantly telling me that essays are like 'chips and twisties', thus meaning that the content of the essay must be answering the designated question, because, ultimately the marker does not care about anything apart from the answer to this question. At the end of each sentence you write, refer back to the question and think - does this relate to the question and what I'm trying to prove?
Altogether, each point should be sought out like this:
Argue your POV.
Support your POV with evidence (do not narrate!)
Analyse your evidence.
Come up with a direct answer to the question (e.g. Stalin's positively did this ....)
And you keep doing this over and over, until your conclusion.
This will make it a lot easier in exams, if you sought it out like this.
Good Luck!