Choosing an essay topic is basically one of the first stages of writing an essay. This is especially the case when no essay topic has been assigned and you as the writer has been given sufficient leeway to choose the topic.
A good starting point may be by examining the purpose of the essay. What do you intend to achieve? Do you intend to persuade your audience to adopt your line of thought or do you simply want to inform them?
After you have determined the purpose, list down all possible essay topics that are of interest to you, brainstorm and evaluate each topic for suitability of the intended purpose. If the essay that is expected is supposed to be a general overview, you can now put pen to paper, but if it is required to be specific, you will have to narrow down your essay topic to as specific an area as possible.
After this you can now write on!
