That's not much to go on. Here are the pros and cons of the main tourist areas:
Kuah
Pros: Good shopping, cheap eateries and pubs. Very cheap accommodations. Good base camp for backpackers if you are renting car or scooter. Cons: No swimmable beaches, few tourist attractions.
Cenang
Pros: Restaurants, spas & shops jammed like sardines. Best eating, boozing and shopping choices on the island within walking distance. Great beach. Most sociable place in Langkawi. Cons: Busy, can get frantic, jetskis buzzing around like hornets. Not very romantic.
Tengah
Pros: Like Cenang but much quieter, more secluded, more romantic. Good walkers can make it to Cenang. Cons: More spread out, less dining and shopping choices.
Burau Bay
Great scenic bay perfect for watersports. Great nature tour opportunities (rainforest at doorstep). Secluded and Romantic as hell. Resorts here are great value for money. Oriental Village next door for dining and shopping. 7 Wells close by. Cons: Might be too secluded for some.
North of the Island
Pros: the best beaches, the most romantic vibe, the best darn EVERYTHING. Cons: Super bleedin' expensive. Remote and far from everything (but then why would you even want to leave the resort?).