Potentially, each of you can have a different test in terms of the questions that you see. There are a significant number of experimental questions sprinkled in as well, and the experimental questions do not factor into your score. It is hard to predict how you are doing throughout the test because you could get a very easy or difficult experimental question out of the blue. You won't know how you did on the prior question, so just focus on doing your best on each question. You'll be penalized for incorrect answers, but the penalty becomes less strict as you get deeper into each section.
People usually approach tests with the goal to finish.
Using this knowledge, ETS designed a test that punishes you for rushing at the beginning. You simply must do your best on earlier questions. Pace yourself, and work on accuracy as opposed to quantity. Finally, let me emphasize that these explanations and strategies are guidelines only. Different goals require different pacing.