For one of my failed attempts, I was stuck behind a street sweeper, which put me off.
My road instincts were still set to 'bicycle' at that stage - bicycle = be wary of EVERYTHING, because it can do more damage to you than you can to it. Flinch when anything is coming up behind. The only way out of that mode of thinking was much more practice.
Get to know your vehicle - size, length, turning points. I advise driving in it for at least half an hour before your test, and practicing your 3pt turns and parallel parking manoeuvres during that practice drive.
Do not switch lanes or try to merge without indicating! It is amazing how many drivers who should know better forget that bit, but it is something that testers watch out for.
When you do your head checks, make them quick, but obvious. Definitely look though, because what you don't see could kill you. Road parity (positioning on the road) can be important.
Also, try to brake gently. My driving instructor warned me to try for gentle, gradual stops, because if the tester is flung forwards, they might mark you down. Foot off accelerator, ease onto the brake pedal when slow enough to coast. The distances depend on the car/conditions of course!
Take note of the street signs, as your tester may either not be familiar with the area, or simply be testing you - I had one lady request a U-turn, but there was a sign saying 'no U-turn', which I pointed out. I have a friend who, on his driving test, had a cyclist that HE could see, but the tester could not! He almost failed for not following directions, until he pointed out the cyclist, who he would have hit, had he followed immediately.
My brother failed when going for his manual test because he stalled the car by accident, and that's an automatic fail. I did my test in an automatic, so I have no manual-specific tips.
I am in Australia, and we drive in the left lane. Thus, I have no tips about right/left.
Best of luck!