There is no public transport on Niue. Renting a car is the practical way to explore the island, and almost all visitors do so. Several car hire companies operate on the island; book ahead, especially in peak season, as the fleet is small. Scooters and bicycles are also available for hire.
To drive in Niue you need a local Niue driving licence, available from the Niue Police Department in Alofi for NZD 22. Bring your home country licence. The island has one main road that loops the coast plus a few inland tracks. Distances are short — you can circuit the whole island in a couple of hours.
The roads are generally in good condition but can be slippery after rain. Many of the coastal attractions are reached by short walking tracks off the main road; a car is essential for getting between them.
Niue Blue and a handful of other tour operators run guided activities (whale watching, diving, snorkelling tours, guided walks). These are worth considering if you want an introduction to the main sites, especially underwater.