Although the island does have a small airfield near the main city of Sabang, it is currently used only for military flights. So, the only way to get to Pulau Weh is by boat from Banda Aceh. Ferries leave from the harbor on the western side of Banda Aceh, about 30 minutes from the airport or 10 minutes from the center of town.
There are generally two high speed ferries a day between Banda Aceh and Pulau Weh. Ferries dock at Balohan on the south side of Pulau Weh. From here, there are always taxis and minibuses to take you to Sabang, Iboih, Gapang or elsewhere.
As noted above, to get to Pulau Weh, you first have to get to Banda Aceh, the capital of Aceh Province at the northern end of Sumatra. The easiest way to get there is to fly. There are several domestic flights from Medan and Jakarta, as well as international flights from Penang or Kuala Lumpur in Malaysia. See the Asia Airports guide to Banda Aceh airport for a current list of flights as well as all the ins and outs ofthe airport.