Hi aviddd,
Based on how you phrased your questions, I assume that you are taking your Official GMAT at a Testing Facility. For the start of your Exam, you will be given a number of laminated sheets to write on and a marker. The exact number of sheets might vary, but it's typically 3 - 6 sheets. You can request new sheets and/or a new marker at any time, but you will have to hand over your current sheets/marker to the Moderator. If you request new items WHILE the Exam is running, then you might have to wait just a bit (since the Moderator will have to come to you) - and you might lose some time. As such, you might find it best to request new sheets during your two breaks.
There is a short orientation at your workstation before your Exam actually begins, so you could potentially write some initial notes at that time. During the orientation, you will also be given the option to select up to 5 Schools to receive your Official Score Report for that Exam. You do not need to memorize any 'School codes'; there will be a search tool that you can use to find the full names of the Schools.
You will have an optional 8-minute break after the Quant section and after the Verbal section. You have to raise your hand and wait for the Moderator to escort you out of the room though (and it takes time to exit and enter the Computer Lab - and those tasks count against your 8 minutes).
The nature of your questions implies that you didn't know how Test Day would 'function' until now. How have you been taking your practice CATs? If you were taking those Tests in a way that was not a match for what you'll face on Test Day (such as taking longer breaks, pausing the Tests, skipping sections, etc.), then your practice results might be 'off.' As such, you might consider pushing back your Test Date a bit so that you can take some additional CATs in a manner that more accurately reflects the specific way that your Official GMAT will be administered.
1) On what dates did you take EACH of your CATs/mocks and how did you score on EACH (including the Quant and Verbal Scaled Scores for EACH)?
2) What is your overall goal score?
GMAT assassins aren't born, they're made,
Rich