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.