Like making a hamburger, writing a good essay takes preparation. Your topic should be broad or common enough that most people will know at least something about what you're discussing.
In the middle, you'll find the hamburger itself. Think of it this way: Like the two pieces of a hamburger bun, the introduction and conclusion should be similar in tone, brief enough to convey your topic but substantial enough to frame the issue that you'll articulate in the meat, or body of the essay.
Follow that with a sentence to introduce your body paragraphs.
This not only gives the essay structure, but it also signals to the reader what is to come.
These ideas don't need to be written as complete sentences in the outline; that's what the actual essay is for.
Once you've written and refined your outline, it's time to write the essay. This is your opportunity to hook the reader's interest in the very first sentence, which can be an interesting fact, a quotation, or a rhetorical question, for instance.
Think of the introduction and conclusion as the bun, with the "meat" of your argument in between. Before you can begin writing, you'll need to choose a topic for your essay, ideally one that you're already interested in.
The introduction is where you'll state your thesis, while the conclusion sums up your case. The body of your essay, where you'll present facts to support your position, must be much more substantial, usually three paragraphs. Nothing is harder than trying to write about something you don't care about.