Since I'm not from GB I haven't done anything like Thinking Skills or something like that before. I guess the only way to prepare for the test is to get a feeling for it by doing the online practise test on the TSA site. Doing it I think I developed a feeling for the way the questions are constructed. I did the online test and it told me that I had reached an overall score of 83%, which I think isn't too bad considering that last year's average score was 63%. But I guess the TSA on Wednesday is going to be much harder than the practise test on the hp.
Good luck everyone on Wednesday!