Depending on the nature of the essay, you want to follow the basic skeleton.
Introduction (with hook, main points, thesis), body, conclusion.
It helps if each paragraph ties in with the last. Like, for example, the conclusion sentence of your first body paragraph should tie in with the introduction sentence of your next body paragraph, and so on and so forth. You should stick to (but not be afraid to refer back to other points) one point per paragraph.
Essays always need voice - if they're personal or professional.
Don't ramble and consider your audience. If you're writing this for little kids, don't use words they wouldn't understand, if you're writing this for class, don't use terms little kids would use.
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