Camping isn't encouraged outside Lanai's one official campground at Hulopoe: the island is privately owned; islanders are keen on privacy; and, unless you know about local conditions, camping on the beach can be hazardous.
Castle & Cooke Resorts Campground. The inviting, grassy campground at Hulopoe Beach has shade trees, clean restrooms, barbecue grills, beachside showers, and a big grass lawn, perfect for Frisbee. All of that and it happens to be a stone's throw from one of the best beaches in the state. (Camping on the beach itself is reserved for residents only.) Buy charcoal in Lanai City, as well as basic camping supplies and food. Cutting firewood is not allowed. It is possible to walk from Manele Harbor to the campground. Call in advance; it's $20 for a permit, plus a $5 fee per person per night (three-night limit). 808/565-3273 for permits and advance reservations.