Your essay should begin with a general statement. Imagine your essay question is: "Smoking should be banned. Discuss both sides of this argument." Your first sentence should not be too specific. For example, "Smoking causes many problems" is not a good first sentence for your essay. It is too specific. Try to think of something more general. For example, "Many people in the world know someone who smokes", or "There are many factors in the world that can affect our health". These kinds of sentences give a more general introduction to the topic you are going to talk about.