Kevin Ching says:

The first thing about planning scenery is to decide the area of the country that your layout would represent and get some photographs so that you can have some ideas of the general terrain. a mining town could represent a small town in that area whether it be coal, ore or some other type that a train would stop and take the produce from that mine to another town for processing and selling on, then bringing back to the mine products that they would use, like wooden beams etc.. Also keep in mind the time frame so that the rolling stock and loco’s match up no use having diesel engines prior to them being introduced in real time if you want to keep it looking authentic