Lamma is the closest of the outlying islands to Central — ferries run roughly every 30 minutes and take 25 minutes. No private cars are permitted, which makes the pace immediately slower.
The island has two main villages. Yung Shue Wan in the north is where most expats live and where the ferry from Central arrives; the main street has bars, cheap Thai and Indian restaurants, and a laid-back atmosphere that is entirely unlike anything on Hong Kong Island. Sok Kwu Wan in the south is smaller and centred almost entirely on seafood — a row of restaurants on the waterfront where tanks of live fish, prawns, crab, and shellfish line the entrance. Pick what you want, agree on a price, and specify how you want it cooked. The ferry to Sok Kwu Wan runs from Aberdeen on Hong Kong Island as well as from Central.
A well-worn hiking path connects the two villages in about 45 minutes through low hills with harbour views. The walk is shaded, easy, and one of the better things you can do in Hong Kong on a clear day. Combine it with lunch or dinner at either end.