There's no bus service on Niue, but taxi services are available. Hitching is easy along the west coast, but you could get stranded on the east. Don't underestimate the size of this island: it's a long, long way to walk. The road around the island is 64 km and the pavement doesn't extend beyond the west coast.
Several companies rent cars, trucks, vans, scooters, and bicycles. On a weekly basis you usually get one day free. Car rentals include kilometers but insurance is often unavailable.
Before heading around the island on a scooter, make sure the tank is full and ask the renter if you can make it on one tank. All rental vehicles are in short supply, so don't wait until the last minute.
A Niue driver's license must be obtained at the police station (no test required if you have another license, it's purely a revenue-generating opportunity).
Driving is on the left and speed limits are 40 kph in the villages or 60 kph on the open road. A stiff penalty applies if you're caught inebriated at a roadside breath analyzer test.
Hanan International Airport (IUE) is three km southeast of Alofi. Some accommodations offer free airport transfers, while others charge a fee. Otherwise it's fairly easy to hitch a ride into town. There's no bank or duty-free shop. An airport departure tax is collected.