An overview is the most effective way to start an essay. In an overview, you give a succinct summary of the big picture of the text (poem, play, story) focused through the requirements of the question. You also say what point of view you hold concerning the question - that is, how you intend to answer it.
As well as outlining how you will answer the question, the overview should tell which text(s) you will use to support your answer (unless this is obvious), and provides a summary of what the text is about and why it was written, also mentioning briefly, any significant details of its author's context and motivation.
An effective overview acts as a kind of 'springboard' from which to launch into the essay proper - and having already covered in brief the general WHAT and WHY of the big picture of the text, the essay can then move into what gains most marks - your analysis and discussion of the text's significant EFFECTS, the author's METHODS and REASONS for creating these.
It is a useful technique to integrate fluently into your overview a word or phrase from both the question and the text - not forgetting to use speech marks around any quoted words. This immediately suggests a close engagement with the question and the text and shows great confidence.