The NZ AIP has the answer.
5.1.2 The following procedures should be followed by pilots:
(a) If the aircraft is RTF equipped, advise aerodrome traffic of joining intentions.
(b) Approach the aerodrome by descending or climbing to 1500 ft or above aerodrome elevation. If a circuit height other than 1000 ft is specified on the aerodrome chart, join at not less than 500 ft above circuit height, or if applicable, the specified joining altitude.
(c) (c) Pass over the aerodrome (keeping it on your left) in order to observe wind, circuit traffic and any ground signals displayed in order to establish the runway-in-use and sequence safely; if these cannot be fully ascertained, continue (wings level) to a point beyond the circuit area (approx. 2 NM) and turn left to return to the aerodrome at or above the joining height as specified in (b) to reassess circuit direction.
(d) Once the circuit direction is established, make all subsequent turns in the direction of the traffic circuit.