A good essay answers the set question, conforms to the word limits and other directions set by the assignment and is as concise as possible, avoiding irrelevant or extraneous information that distracts from the main argument.
Good essays also indicate the evidence on which any argument and individual points are based and acknowledge the sources of information, if appropriate.
Some students will have a better command of language and a wider vocabulary than others, but that is less important than the ability to get your message across clearly. Use words that you understand and are comfortable with. It is far better to say what you have to say simply than to attempt to dress up your information in flowery prose.
Finally, be sure to edit your work for spelling and typographical mistakes before you hand it in. Sloppy work at this stage detracts from what might otherwise be a good essay.
