Catch a Fullers Ferry to Rangitoto Wharf from Downtown Auckland or Devonport. Make sure you get back to the wharf in time to catch the last ferry back or else you will be stuck on the island overnight or have to call up an expensive water taxi!
Do not fall over on the track up to the summit as the fresh lava can be sharp. Wear sturdy footwear, not jandals or bare feet. Stay on the track - it is dangerous to walk over the sharp and rubbly lava flow surfaces. In summer take sun tan cream and water to drink as it can get hot crossing the lava flow fields. There is no shop on the island.
If you plan to enter the lava caves take a torch and something to protect your head from being scraped on the unforgiving lava roof.
The lower parts of the island are accessible by wheelchair. You can buy a ticket on the tourist tractor train that will take you on a circuit around the island stopping near the top for the more able visitors to climb the stairs and boardwalk to the summit of Rangitoto. The best way to see the island is to take the walking track up to the top from the wharf but the track is a bit rough under foot for those not used to rough terrain and the ascent up the scoria cone is moderately steep.