The other day I was ambling along and a semi-hipster on a cruiser passed me and gave out the obligatory "On you left." As he passed he said, "I need a bell." I dinged my bell in response and when I passed him a a bit later, he said "bell me, man." I did and concluded that bicycle bells are a much more civilized way of announcing passing because they look nice and make a lovely, peaceful ding.
You can mount them any way or where you want.