You can come to Langkawi by 2 ways: 

1) Airplane 

2) Ferry 

There are ferry services connected from the mainland (Kuala Keday, Kuala Perlis, Penang, Satun) to Langkawi operated everyday.

Most people only stay at hotels near Kuah Town (map: bottom right) and Pantai Cenang (map: bottom left). Most luxury hotels are situated in Pantai Cenang. Because of the beautiful beach scenery, many people chose to stay there. Pantai Cenang is more happening at night. As for Kuah Town, accommodation here is slightly cheaper and it is nearer to most of the tourist sites.