There are definitely some key steps to follow to write a good factual essay. The first is to decipher the question: what specifically are they asking you to prove or disprove or explain. Think in terms of who, what, when , where, why and how. Highlight key terms in the question.
Next TAKE THE TIME TO OUTLINE! Break the question into parts. Then break each part into what facts and examples you have to support the answers. It can be a simple list. If the question is a single part question, decide what facts and examples you have to answer the question and write them down. Put them in groups if you have many. Make a few notes about the details of each fact and example and how they answer the question.
Now write the middle of the essay first. Each paragraph and section should start with a good overarching sentence to introduce that topic, then explain and connect your examples. Sum up by restating (or stating) how these examples correctly answer the question.
Move on to the next set of examples or part of the question.
Once you have fleshed out the middle you will find the introduction and conclusion easier to write. You know what you are presenting as an answer and can generically introduce your answer and where you are going with the essay in terms of specifics. The conclusion is simply drawing back together how all your examples prove the point and maybe bring up other connected points.
Hope this helps.