Firstly, when you failed last time, they should have de-briefed you about where you went wrong in your interview. As an overview - no matter what anyone says about 'be yourself' - be aware that the interview is designed to place you under pressure; the first question: how old are you in years and months, isn't the kind of thing somebody instantly knows (do they?), so it's designed to pressure you.
The rest of the interview is broken into 2 halves; in the first bit they'll look particularly for gaps. If you spent 6 months after your A-levels lolling around doing very little, they'll exploit that and dig into the subject. Other obscure questions about what you spent your pocket money on when you were 13 can be prepared for (again, not something I instantly remember!), so have an answer.
Bottom line is, be honest with yourself and look for
any potential gaps the interviewers can exploit and have an answer/explanation for them. They're not necessarily wanting to hear you spent your pocket money on walking-sticks for old ladies and you run the school bible club, but anything controversial will be latched onto. That said, something like hitch-hiking around Europe for a year can be turned to your advantage if you pitch it as expanding your horizons, self-dependence etc.
The second part is your knowledge of current affairs, the military etc. As well as knowing about your preferred branch, research what it means to be an officer - they'll ask what you think about being nobbled for dull secondary duties and want to hear how you view an officer as being 'a general decent chap who never stops thinking about the RAF'. If you've put a third choice on your application form
research it! because they'll expect you to know everything about your first couple.
Learning everything you can about RAF bases and aircraft goes without saying!
Current affairs is another potential trap; they'll ask you what's in the news and, once they see you know something about a particular subject they'll cut you off and ask 'what else?' I suggest you go in-depth with about 5 main subjects (so they eventually get bored by your broad knowledge!) and, if you don't have much in the way of opinions, get some! (newspaper columns are good for opinions; just make sure they're not too radical ie. we should never have gone to war!).
Other minor tips: don't bull**** because they'll spot it and help you dig; don't waffle about something you don't know about (same result). If you don't know something, say so!
Also, don't go in there with a 'begging-bowl' approach; to a point, fight back if they put you on the spot - shows spirit ahhh!
As for aptitudes and stuff, get 'Know Your IQ' by H J Eysenck as it gets you in the frame of mind for the tests and practice time/distance/speed questions, so you're under less pressure in the leadership situations. By that I mean you'll be able to concentrate on the task in hand, rather than get buried in the nuts and bolts of 'how long it will take a landrover to get from A to B via route F, avoiding the flooded road between 1000-1300, with it's speed reduced by 50% at night' kind of stuff!
Good luck!
