When there's walls or barrels, I like to walk around the outside of the props to make sure there's noting I'm not seeing. Sometimes look at the stage backwards from out by the berm. Even then, there's times I just don't see things.
I once shot a stage with a blazing fast time. One of those ones when you hear the time you think :Hmm... that's too fast". Missed a whole four target array. It wasn't hidden, it wasn't through a port, it wasn't even far away, it was wide open and only about 7 yards off the FFZ. It was a simple stage. I'd had my hat cam running through the whole thing, even through the walk through. Watching the video, I air gunnedI right past the array four times without seeing it, looking and turning left when I needed to turn right, then I shot it just like I walked it.