Finding shipping
is somewhat random, but you can improve your chances by thinking about where shipping ought to be and concentrating your searches in those areas. "Choke points," such as straights and bay entrances are good places to begin looking, and anywhere nearby a port city is generally somewhat productive. The patrol areas are usually near at least one of those two features.
Also, it helps to have an idea where the shipping lanes are. I know there is a great map in TMO that displays a lot of them, but even without a map figuring them out falls somewhat into the realm common sense. After all, ships, and their sailors go from port to port.
