If you are talking about a type of essay, then you need to break down the type of essay a little bit here. Expository writing is a traditional type of essay in which you present facts and opinions with support from examples or research. An analysis essay analyzes something. The "thing" being analyzed may truly be anything! You could write an analysis essay on a piece of literature, an historical event, a type of car, a political policy, a law, a social issue etc. If you are writing an expository essay that analyzes something, then you first need to determine your topic and then more importantly, define your thesis. Ask yourself what you are trying to prove about that topic. Once you know what you intend to prove, then you need to plan your research and organize your ideas into logical paragraph divisions.