The difference between a slow afternoon and a busy one is rarely how good you are. It is where you were standing.
Follow the footfall
Broadway takes most of the city's visitors, and it does not stop. If you want volume, that is where volume is.
The quieter places are not worthless
The Hermitage sees about 190,000 people a year rather than millions, but the people who go there have planned the trip, and people who plan a trip want a photograph of it.
Light beats footfall after five
Late in the day, the pedestrian bridge is worth more than a busier spot with worse light. You are selling a photograph, not proximity.
Stay where you can be reached
A request goes to everybody nearby. Being fifteen minutes away is the same as not being there.