Do I need to book weeks before I want to go to Pearl Harbour or just arrive on the day?
It all depends on what you want to do. There are various sights within Pearl Harbor.
If you want to take the Arizona Memorial tour ... then yes, you do need to plan in advance. The occupancy is limited. https:/…index.htm
Don't pay for a commercial bus tour. They are just expensive transportation. They do not "lead" tours.Edited: 10:55 pm, June 08, 2018
Assuming you are going to stay in Waikiki and are talking about a day trip from Waikiki, you can either:
Make advanced reservations for USS Arizona Memorial (best option):
Just show up at the Visitors Center by 7am the day you go and get walk up tickets.
Thanks so much
You need to check though. The Arizona Memorial is currently closed, with no reopening date announced. There were structural issues that made the officials deem it unsafe.
There are still tours that go by the Memorial.
The Navy still takes you out on the launch to see the memorial just like they do all the time. At this point you won't be able to disembark onto the memorial itself. Still worth going for this moving experience.