The best place to stay is at a Sandals Resort in St. Lucia. They provide the best service and amenities. One of the best parts is it is all-inclusive so all the meals, drinks and snacks are included in your package. There are three Sandals resorts on the island. We stayed at the Grande St. Lucian, the biggest of the three. We got the views of both the Caribbean Sea and the Atlantic Ocean.
We booked some tours through the resort. We went dolphin/whale watching, which were plentiful (AWESOME!!) and also got a nice view of the island from the water, where we saw the Pitons and the volcano, as well as many remnants from the wars. We got to learn a lot about the history of the island and got a bunch of amazing pictures! We also went hiking on Pigeon Island National Park, which is a 5 minute walk from the Grande. This is a national landmark from the war when the French and British were fighting. There are a bunch of old buildings still there and Fort Rodney. It is quite a workout to make the climb but well worth it. The views cannot even be described - absolutely breath taking of the Caribbean. On a clear day you can see the island of Martinique to the North and the Pitons the South, as well as a full 360 view of the water and island.
A last must is to take the helicopter ride to the airport instead of the shuttle! It is only about 15 minutes, compared to the 2 hour bus ride, and you get some more amazing pictures and views. It is an awesome experience. Flying over the rain forest is wonderful. The bus ride is cool because you get to see the locals and how life is for them, but it is kind of a bumpy ride.