Passed first time, after driving for 5 months. My advice is, relax. First of all, if you have your own car, use it rather than your instructor's. It shows your examiner that you know how to drive your own car safely, not just the super power-assisted car your instructor uses. If you are inclined to drive aggressively or slightly fast, tone it down. You might know you're in complete control, but your examiner doesn't know you, and his life is in your hands. You don't want him to feel nervous at any point. Don't take it to the other extreme either. If you hesitate too much and drive too slow, he might fail you for that (though he might understand that you're just being extra cautious). Pay attention to your surroundings. If you go over a speedbump too quickly, tell him 'oops, that was a little too fast'. It shows you knew there was a speedbump and were paying attention. If you make a mistake, might be worth mentioning it (unless you were speeding, in which case slow down and hope he hasn't noticed :P). CHECK YOUR MIRRORS. Especially for motorbikes and bicycles. Even if you've never seen one while practicing before, chances are there's going to be one just for your big day. You want to show you can drive safely and calmly and are aware of your surroundings. What you do after you pass is up to you.
I really didn't think I'd pass first time as my older brother had failed 3 times before passing, so I just went and thought to myself, 'ok, this is like a mock exam. You don't have to pass first time, just do your best and try to make the least number of mistakes as possible'. I was super surprised when he counted up my numerous minors and casually said I'd passed.