I have had a very hard time sorting out how to group industries. I would like to try to keep majors by themselves and smaller ones such as brewerys near towns…
Then I realized I cannot make up my mind without suggestions from you all… I have thought out 3 to 5 towns using different siding and passing tracks for the local economy and they all depend on the city for goods, food passengers etc.
For example one of them is going to be a time saver plan for about 3 industries. Should I keep this all agricutural such as dairy, wool and cattle?
It depends a lot on the general theme of the layout and the era. Until the mid-20th century it was not unusual for industries of various types to be located in cities and towns, at least on the outskirts, with homes and businesses nearby–and the industries do not necessarily have to be related.
Era is important too–if your layout is set before automobiles became common, there will be homes and businesses close to industries, or some means of getting employees to work (passenger runs, trolleys, etc.) will be required–or, if it’s a really remote location, some sort of camp (like a lumber camp) will be adjacent to the industry.
Keep in mind the flow of products–grain silos in rural areas implies grain mills, breweries and ranches which will receive grain for use in turning into their respective products. Coal mines will send coal to power plants or other distribution points. Agricultural industries (canneries, etc.) will need sheet tin for cans, boxes (wood or cardboard) for shipping, tank cars of corn syrup, etcetera. You can, of course, use an interchange track to bring in goods which aren’t produced by the industries on your layout, or bring them in via a staging area–but it’s still good to know what “non-local industries” ship to your layout–and what products can, in return, be shipped off.