Make notes of problem questions
No matter how proficient you are at the written exam, there are sure to be some questions you aren't certain of. If the department has given you scratch paper to work with, take some quick notes of the questions and answer options and take the scratch paper with you.
This may not be allowed for obvious reasons, so I always carried my own pen and paper folded up in pocket to immediately write down as many questions as I could recall as soon as I walked out of the test.
Don't wait and think you will remember it. If you're like me you will forget. Take extra time after completing your test to reread and remember any questions in the exact manner in which they appeared in the exam.
Wording can be everything, so remembering the exact question and answer options is important. I used to then take these questions to several different people to try to determine the correct answer and do my own research on it if I could.
I would often run across these same questions or the exact same test again and was now confident that my answer was the right one.