The first time I tested I was tempted to tell Sensei that i wasn't ready, but I decided that he knows better than I. I actually trembled from anxiety and my iriminage was pretty sloppy but I passed. The second time I tested I had just gotten out of the hospital. I was very anemic and they were still considering whether or not I needed a transfusion. On top of all of this I hadn't been practicing regularly for a while because college has gotten in the way.My dojo mates went out of their way to prepare me for the test. We met on off days and ran through the test over and over. On the day of the grading my plan was to take it slow and make sure that I was performing smoothly and correctly. I screwed up a couple of times, but I passed. I guess my advice would be to try and remain calm and slow it down. As a wise music teacher once said, speed is the last ingredient.
I think some of the best advice I got was after I passed my shodan. Sensei told me "well, now you've got it, train hard and make sure you deserve it".
Actually passing the grading isn't what matters so much as showing that you deserve it afterwards.