Making up Trains

What were/are the considerations for making up freights and mixed trains on typical NG operations like the D&RG, C&S, RGS? Id guess that foremost was trainorders and delivering cars but...
Did operations on different grades and track factor into the decision where certain cars were in a train? Like heavy coal cars or tank cars.
Did preparing for doubling a hill or cutting a helper in go into the planning.
Did Passenger comfort on mixed trains factor in?
What about livestock cars?
Cabooses sometimes were seen in pairs, some at the end, some after the tender and sometimes in the middle...
In general, were certain cars placed in a train for any other purpose than waybill operations? Most of the photos Ive looked at dont give a clue as to any order to car placement. Sometimes cars are obviously grouped (livestock) but I have seen photos with any number of configurations...
Thanks,
Brian