Few things -
1. You ONLY need to carry a passport and NO printout of the appointment is needed.
2. Before you start the exam, ask the proctor if he/she will tell you the time remaining during breaks. My proctor was nice enough to do so.
3. Some centres have a clock in the locker area. If not ask if there is a clock somewhere. If they do have one then lucky you!
4.Turn off your phone n put it inside your bag. Take your snacks out of the bag and place them out of your bag but inside the locker. This is to make sure that they don't assume you are reaching for your phone when you open the bag during break.
5. As soon as you hand over your passport and they enter your details, they expect you to begin your test. There was a guy pleading to give him 10 min because he was nervous, but they did not allow him to sit in the lobby cuz his details were already entered.
6. You get only 30 seconds to read quant and verbal instructions. You cannot make your ABCD grid and write timings and some extra info you need because those 30 seconds will pass in a flash. So keep it minimum. Maybe just write timing.
7. You will face anxiety. IT IS Okay. Everyone feels it during the test. When you feel like you are reading the same line again and again but nothing makes sense to you, just STOP. Take a deep breath and start over.
8. Leave your ego at home. By ego I mean the ego of not letting go of a question. You will face questions that seem simple but you just cannot solve them at the moment though you know you can. It's okay. Just move on. Guess if it takes more than 3 min.
Finally. Good luck!
We are rooting for you!