From NZ Your Way.com
http://www.nzyourway.com/tips.asp

Electricity
Electricity is supplied throughout New Zealand at 230/240 volts (50 hertz), although most hotels and motels provide 110 volt AC sockets (rated at 20 watts) for electric razors only. 

Time
New Zealand is 12 hours ahead of GMT (Greenwich Mean Time). In summer, on the first Sunday in October, New Zealand has daylight saving when clocks are put forward one hour. Daylight saving finishes on the last Sunday of March.

Driving
Most foreign driver licences are acceptable in New Zealand (check with your travel agent). New Zealanders drive on the left, give way to all traffic crossing or approaching from the right. Most rental car companies will provide a short list of the more important rules.

Tipping
Tips in New Zealand are optional and are generally given in appreciation of extra good service. You should tip 5-10% of the bill in a restaurant (not in a simple café) if you feel you have received exceptional service.

 

New Zealand Travel Information Network
http://www.nzti.com/keyfacts.htm

Tipping and Service Charges
Normally New Zealanders do not expect tips for service. However, tipping for extra special service or kindness is at the visitor's discretion. Hotels and restaurants in New Zealand do not add service charges to their bills.