It depends on the camera, for an SLR it's the Jimmy Page long guitar strap look but for a rangefinder I go for the geeky surf guitar high on the chest look. Each is actually more about how I carry the camera when I'm not pointing it at a scene. I was taught at college if you carry a camera on your shoulder the lens should face inwards so if the camera swings out it's only the back of the camera that can make contact with something. A short strap on a light camera like a Leica means you only need your upper arm to hold it secure lens inwards, but for a heavier SLR it's good to use your elbow to do the same.