Depends on what your worst section was.
If it was reading/writing, read the NY times or something equivalent to gather a quick and basic understanding of higher level reading/writing. Also, this vocabulary list can offer a speedy improvement to your vocabulary:
If your problem was math, look at this site: http://www.erikthered.com/tutor/facts-and-formulas-1.pdf
This provides an overlay of formulas you’re likely to see on the SAT and what you can quickly glance over, considering the next SAT is this coming weekend.
For the essay, memorize this formula when writing. SAT graders don’t only want to see penmanship, skillful wordplay and varied sentence structure, but also (and frankly above all else) organized thoughts.
Open with an intro, a thesis, and a reason why the grader should freakin’ care. They’ll be reading the same essay over, and over, and over again. Make yours stand out; give them a reason to notice.
The first body paragraph should relate your thesis and your answer to the question posed/argument for or against to a book or play you’ve read. Show the grader you’re edified and well versed in modern culture.
Next, relate your thesis to a significant historical event or a meaningful person. For example, Martin Luther King and Gandhi work wonders.
And finally, if you have the time, take your time to fluff and draw your reader in. Add a personal experience. This is the last and frankly optional paragraph because if you don’t have the time to finish, the grader won’t care.
But if you do, dial it up. Show that you’ve lived a bit, that you’ve learned and pushed through adversity, that you’re a person worthy of consideration in the eyes of the almighty college board.
I followed this basic structure all three times and scored a 12 on each essay.
Remember to vary your sentence structure, verbs, and adjectives. And don’t forget transitions. Make things flow smoothly like a fresh pint of Guinness or like the skin of a velvet swatch.
As for the SAT as a whole, don’t freak yourself out. You can handle it; the test is written for your success, not to see you fail. Hell, the college board won’t get paid as well if no one can pass the test. They aren’t trying to trick you, so don’t stress yourself out by looking for loopholes if the answer doesn’t appear immediately.
I wish you the best of luck, whenever your SAT may be.