"Broadcast"
The "Broadcast" segment's best hiding spot is in an isolated building across the parking lot from the abandoned Russian television station. It's a perfect sniper location. The hole in the upstairs office wall gives you a superior vantage point. You can easily shoot down enemies on the station roof or the second floor of the lobby, and still cover most of the parking lot. Place a claymore by the entrance to the stairwell so no other player can sneak up on you.
"Downpour"
The large barn that sits across the dry creek bed is an ideal place to stage an ambush in "Downpour." Most players will try to avoid crossing the bridge that spans the creek due to the poor cover it provides. The alternate route across requires opposing players to enter the barn to maintain their cover. The barn's shadows will conceal you from any player transitioning from the bright sunlight outside of the barn to the structure's dark interior.
"Creek"
"Creek" has a great hiding spot in between the small row of houses and the large valley. You can reach it from the house on the right side of the screen with the picket fence. On the second floor there's a short stairway that takes you to the attic. The hole in the attic wall gives you a vantage point that covers the ridge along the valley's wall and most of the slope close to the row of houses.
"District"
Find the staircase inside the market that leads up to the pathway that over looks the bazaar. Follow the wall that runs parallel to the bazaar until you reach the door at the end. Jump on top of the wall so you stand overlooking the bazaar, and then jump to the wooden post directly in front of you. Move along the post until you reach the opening to the bazaar. You will be able to cover the entire bazaar from this hidden spot. Unless opponents physically see you, they will have no way of knowing where you are firing from.