Operations 
A methodology for getting lading from a Source to a Destination without accident.
Operations
People who chose model railroading may of course be craftsmen first. They may build what is essentially a diorama, with the showcased objects being trains rather than automobiles, ships, airplanes, or tanks (which of course can all make an appearance on a railroad layout). The works of the most talented of these model artists are heavily featured in magazines and videos.
However quite a large segment of the model railroading community are not model builders, either due to a genuine lack of talent, or most likely because model construction holds hardly any interest for them (ergo why they chose 3rail R-T-R trains in the first place). They are problem solvers, who enjoy puzzles and keeping things flowing smoothly. To them dispatching trains on a layout is a dream assignment; and designing timetables, planning car forwarding movements, and studying track layouts offers a relaxing way to spend an armchair railroading evening. For this group Operation (as opposed to just building) is the whole point of having a layout, and so running 3rail semi-toy trains past crude mockup buildings is just as pleasant an experience as were they running museum quality trains past photo-realistic buildings (and certainly more affordable).
All functional layouts (as opposed to animated dioramas) will necessitate Operations. For operations to be effective (avoiding accidents, delivering simulated goods efficiently, making moving model trains fun rather than frustrating), everyone must know where the trains are, where they came from, and where they are going. A helpful planning tool is to create a Service Schematic [EXAMPLE] for the area modeled on your layout.
Real railroads have evolved their operating methods over two centuries, and their methodology is probably very different of what you are experiencing elsewhere in your daily life. As such, initially you should just dip your toes by Keeping It Somewhat Simple [EXPLANATION], so as to prevent becoming overwhelmed by prototype operations minutia [ESSAY]. Traction railways operate in a manner similar to conventional railroads, only their traffic separation is less and their operating rules are much looser. Signaling is however more crucial, so it is strongly encouraged that a working trackside signal system (including automobile traffic signals/signs where street running) be modeled.
"Operations" is actually an inclusive term covering two distinct but related requirements: 1-Profitably forwarding lading, while 2-preventing traffic snarls (especially accidents).
1= Assigning and Routing cars (i.e., Forwarding [EXPLANATION]) will always require some planning to accomplish, as the lading needs both an appropriate car, and a strategy to get the lading from the shipper to the receiver in a timely and cost effective manner. On a model railroad the simplest (but most unrealistic) way to Forward is by employing the Random Car Forwarding method, whereby you scan the layout for empty cars of a suitable vehicle Type to send to Shippers, and for suitable Receivers to accept loaded cars. More technically savvy modelers can program a computer to print a SwitchList, which states the exact cars to be taken and left by the train. The beauty of O-scale is that the identifying markings on individual cars are easy to read.
2= An easy way to eliminate any traffic issues is to only run one locomotive at a time on a closed section of track. Only when the railroad must cross another railroad, or if more than one locomotive occupies the tracks, does communication become critical. Prototype railroads communicate by sending messages both statically (such as through Rulebooks, Timetables, and Orders/Warrants), and in real time (such as through trackside Signals and Radio).
Operations on your layout should not always occur on a Summer Tuesday Afternoon. For variety intentionally shake things up by operating into the night, or pretending the day is a weekend or holiday. To inject a bit of additional play, the scenery can also be altered slightly to emphasize that something is different. For example: Dim the room lighting and illuminate structure interiors during operational evening hours. Add some flags or decorations to your streetlight posts to suggest a holiday. Place extra parked vehicles at a business whenever extra train cars are called for. Run a Maintenance-of-Way train, or use your "five-finger-crane" for that sense of accomplishment [EXAMPLE] you get from transferring piggyback trailers and other swappable loads from rollingstock to trucks.
As you add more locomotives or desire to move goods in a more realistic manner, you can slowly begin incorporating more prototypical Operating methods. For the most part on your model (unless it will add a desirable quirk), you should ignore prototype railroad regulatory and labor compliance burdens.
All content appearing on this webpage is FREE for personal use, being either expressly created or previously posted as anonymously accessible public on the Internet.