Go to the circular building and look through the stair entrance. There is a hut with two rectangular windows overlooking the sandy area that can be used as a sniper position. Also, there is a tall building on the water with windows overlooking the entire map that can be used.
Go to the little room at the bottom of the map (with the ladder), and jump across the walkway. You should be on a very thin log-like object. Proceed on the thin piece of wood and you will eventually reach an area. It is easy to snipe people from here, and no one will think someone would be there.
At the house where the Marines begin, as you go outside there is a set of stairs. Crouch beside the stairs and you will blend into the bushes. This location gives you a good view of the tower and the ocean.