That is a huge obsession of mine. I am so afraid of doing bad on a test because I mislabeled my scantron. I always take the test like 2-3 times. I go through it the first time and bubble in all my answers on the scantron and circle the answer I picked on the test page. At the end of each page, I check the number of the question that I am on and make sure that I am on the same number on the scantron. When I am finished, I go over the test again without looking at the scantron. If I make any adjustments to my answers (which you should almost never do unless you are absolutely sure), I immediately change them on the scantron. After I finish going through the test the second time, I double check my answers on my test sheets against what I bubbled on the scantron. Every now and then I find that I am off track, but I have yet to really mess up bad (knock on wood). The worst thing that really happens is I read the questions so many times that I start to second guess myself and I change an answer that was otherwise right. But it has worked so far so good, I have a 4.0 to show for it.