I resat my test recently and was amazed at some of the things i'd been told when first i sat my test 10 years ago that simply werent true.
Back when i was 17 my instructor had insisted that you couldnt cross your arms and had to sit there feeding the wheel round with your hands at 10-2, which it turns out is a load of ********.
I'll happily admit that when i first sat my test i couldnt really drive. Sure i could propel the car along pretty well, and thaught i was the dogs dangly bits, but in real terms, my awareness and whatnot were nowhere near where they end up after you've got a few years under your belt.
The biggest thing the instructor pulled me up on this time round was mirrors. They want to really see you checking them at specific times. Slowing down for a junction or roundabout is fairly obvious, but things like changing speed limits should also have you checking the mirrors BEFORE braking/accellerating to the new speed. Also, when pulling out of a junction, they again want to see a mirror check as you straighten up on the new road, just incase somethings coming that you havent seen. Similarly when driving along, you should be checking the rear view every now and then, to ensure your aware of whats happening behind you. You should get into the habit of doing this, and continue doing it, rather than just ticking the boxes for the examiner, as it will make you a much better driver in general.
90% of driving is awareness of your surroundings, physically driving the car is such a small part, but new drivers tend to spend a lot more than that thinking about actually driving the car, which makes paying the required attention to the road that extra bit difficult. the number of drivers i find on the road that simply have no clue whats going on around them is unreal. They're simply fixated looking out the windscreen and completely ignore everything else.
Also, stay calm! Even if you think you've ****ed it up. Back when i sat my original test, i sort of pulled out on a guy at a roundabout. The guy came flying round at ludicrous speed, as i'd already started moving off, and i kept going. I thaught i'd failed, and it made me panic, which resulted in me stalling out at the next junction. After i'd completed the test, sure i was going to fail, the examiner said i'd passed, and he'd only given me a minor for the roundabout incident because in his eyes the only thing i'd done wrong was change gear instead of giving it an extra bit of poke in 1st to get out the guys way.