Own the topic. You can speak freely and interestingly only about what you really know. Therefore, before writing on an unfamiliar topic, study it, including interesting little-known details and nuances that may attract attention.
Define your message. When you know the subject, you must decide, what do you want to tell the world about it? What is your attitude to it?
Consider the structure. Will you talk about the most important things first, and then the secondary things, or is essayhave legit? The structure helps you to arrange your thoughts in a logical sequence. This is especially important in essays, since many people "drown" in free form and emotionality.
Keep in mind brevity. Despite the abundance of information and thoughts you want to express, do not overload the text. Do not use more than 2 arguments to prove your points. Describe the problem briefly. Use short sentences.
Do not be ashamed of your thoughts. Use only your own thoughts and reasoning in the essay, even if you want to appropriate someone else's more "intelligent" opinion. The essay is your reflection, your thoughts and reasoning.
While working on an essay about UFOs, even if you completely agree with the opinions of famous ufologists, do not copy their ideas, because the readers of your essay are probably familiar with them, too. It is enough to mention their names and works, but your own point of view.