Even though people say dont automate, I like to have one worker automated on N , network, because it can link up some cities that you wouldnt think of, AI cities, that can give better trade route income. If there are a few wars or barbs around, team the worker with a chariot, or whatever.
In the mid-late game, if you are micromanaging a lot of fighting, you can afford to let a team of three workers automate on A to get the forests lumbermilled IMO (just select "workers leave forests" option in the options menu).
Railroading the mines and lumbermills of the big prod cities should be done manually though.
Also the N , network worker will railroad the continent when railroads come in. It's good to have it all railroaded for fast defense.He can have a machine gun escort. If you want to micro all that railroading go ahead, but it's too much micro for me.
BTW, ctrl # adds that number to the worker, so when you want to find him you just press #. thay cant get lost.