Rotation....couldn't agree more.
I used to be crap at aptitude tests. I bought loads of books and practiced my little rear end off. The last 2 i took i passed. When people say that your aptitude never changes because you don't...that's b0llocks, as is the phrase "you can do the same tests over and over and you'll always get similar results." I'm not a computer.
I have taken the same aptitude tests twice. The first time, i screwed up. The second I stormed them. I was 2 totally different people. I used different approaches to tests i wasn't very good at and also practiced at them more than those i was comfortable with.
Try treating them as practice tests when you go. You might relax. Also, don't think that the really clever looking bloke is better than you. He might not be. It's YOU against the system. (ooh, that'd be a cool line in the matrix
)
Never quit...no matter how badly you think you're doing.
I met some guy at oxford who had just finished his IR, he was 23 and had paid foor it himself. I asked him why he didn't try for a sponsorship, he replied 'I tried a 3 times but kept on getting rejected at the aptitudes'....sorry but what a loser.