My understanding was that it was rare to pass first time? Anyway, neither here nor there! It was on my 3rd (and final) attempt that I got through. My first application was at 17, not even finished my A-Levels... I remember that at that time, stage 1 was an (almost) all-day affair where they did the personality questionnaire on paper.
Second attempt was last year and got to stage 2.
Between last year and this year, I looked at what I had done and remembered where I had let myself get annoyed with mistakes. Going in this time, when I made a mistake it was a grunt of disapproval, and forget about it.
If you're truly enthuastic about it, it'll show.
I think I've rambled a bit, but anyhow!
Good luck!