Unless if you finished way ahead of schedule, don`t worry about major revisions like reorganizing the structure of the essay–it`s better to hand in an essay with an imperfect structure than a paper that`s impossible to follow because you had to stop halfway through the revision process.
However, it`s important to keep in mind that your professor understands the circumstances under which the essay was written. They`re fully aware of the time pressure you were dealing with, and they will judge your work far differently than they would judge a typical essay with a deadline set weeks after the assignment date.
You should formulate your thesis statement—the central argument you`re going to make. The thesis statement provides focus and signals your position on the topic. It is usually one or two sentences long.
For this reason, it can be helpful to simulate the conditions of a timed exam before the actual day: pick a practice question, find some lined paper, set a stopwatch, and see how you do!
Take note of the amount of time allotted for the exam and split it into reasonably-sized segments, leaving some time at the end for revision if possible. Without a schedule to follow, it`s easy to become too focused on a single paragraph and run out of time to finish the essay.
Your best supporting idea – the one that most strongly makes your case and, simultaneously, about which you have the most knowledge – should go first. Even the best-written essays can fail because of ineffectively placed arguments.