On one of my cyclocross bikes I have the bell on the stem.
On the other it is on the bar just to the right of the stem.
If I'm in a situation where I can't safely get to the bell in time, I just start hollering.
Generally I ring the bell when I am well back, and then call out "Bicycle passing on your left" as I get closer. I sort of consider my bells the advance warning, and my voice the real message.
ETA: 3 of my bikes have Incredi-Bells, and one has the lovely Crane bell Newfsmith linked.
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