You have spent at least two weeks studying, so what’s another couple of minutes? Work through the exam slowly and read all the questions before answering them. If you are done before the time is up, look over your answers.
Arrive to the exam on time. Also make sure you dress appropriately. (Don't come in wearing your pajamas, just something you would usually wear to school.) Be sure that you have something to write with. Usually, a pencil will not be provided for you. If you have a difficult time choosing an appropriate outfit, do this the afternoon before the exam!