As to the real engine bell, I only rang it before initiating movement if there were adjacent tracks or footpaths. If I was starting out of a siding out in the country, I didn't ring the bell for the jackrabbits. Approaching crossings, because it was required by law, I always rang it from the whistle post to the point at which the crossing was fully occupied. I also rang it continuously when meeting or passing a train on an adjacent track, and when arriving, leaving, or moving through stations, as well as when approaching and moving past human beings, whether they were railroad employees or not. Another time I used the bell was when passing through neighborhoods at low speed. At high speed, the train makes so much noise, that people usually can't hear it approaching. Also, the Los Angeles Union Passenger Terminal rules required use of the bell when moving within any of the platform tracks.
On the model railroad, I don't use the bell much: when arriving, departing, or passing through the station is about it. As soon as the train starts moving, I turn it off. I ring it continuously when moving within the locomotive facility and for a prudent distance when approaching a private crossing in Caprock yard.
