I took many attempts to clear my G2 road test, but my G road test i cleared at once. The trick is study the examination centre roads a day before the test or earlier, drive on hwy for long until you get a real feel of the hwy, the hwy exits and entry, the speed limits, and the left , right turns on the residential/school areas, always obey traffic laws, no short cuts or guesses while driving, best practices is defensive driving.
My test was only on the hwy, the examiner took me twice on east/west side of the hwy, be sure to know how to Enter the hwy, follow the speed limit on the ramp and speed up to merge in to the hwy observe check blind spot when safe merge into the hwy traffic, keep on right lane, unless told to change lane when it is safe to left and then back to right lane. Exiting hwy follow the speed on the exit ramp and be familiar with emergency parking.
I have enclosed the test sheet which may be of use, to know how the examiner scores. Always check the blind spot, thumb rule is mirror, signal, blind spot before you change lanes.