Mark - Like you, I like to build structures and freight cars, but I like operations equally as well. I do not run any passenger trains since they weren't a part of ATSF operations in my era of 1978-1992. I do not run two trains at the same time, even though it is possible, simply because I cannot keep track of two. I have DC with two throttles, one fixed and one walk-around. I really like switching, I have 70+ industries over the 365' of main line. Staging, sidings and spurs add another 900' of trackage. Additional turnouts are already in place to add more industries when I get to the point of developing those sections of bare plywood. My operations follow two patterns. The first is through freights or drags as some call them. These can be unit trains such as container/trailer, grain, autoracks, plastic pellets, ethanol, vegetable oil, or they can be mixed freights. These I run from one end of the layout to the other. I mostly run them in the middle of running a switching run where I park the local on a siding while I run the through trains over the main. Secondly I run locals. Most of my local or peddler runs are known as "out and back", where I switch one town (10 towns with between 3 and 10 industries each) and return to the staging yard. These can be empties or loads in either direction and always terminate in the yards. Industry to industry on my layout always goes through the yard. I currently use a handwritten switch list that varies every time. I hope to eventually use a switching program that I have that uses either car cards or switchlists (or both) depending on preference. I have two industries that are large enough to have a dedicated switching run, a large grain elevator and an ethanol processing plant. Each have a total of 16 empties going in and 16 loads going out. All ten of my passing sidings have a capacity of 22+ cars and with the exception of five industries, all other industries switch off the passing sidings or additional industry sidings. The main is used in switching operations for temporary parking or for run-arounds as needed. It must be cleared occasionally per the above scenario. I also have an interchange with SLSF to allow for some car rotation.
ATSF did not schedule many freight trains, most were run as extras even though they followed a pattern. They also sent out occasional "sweeper" trains that did nothing but pick up empties along the line. I did not design any "switching puzzles" on my layout, although some thought must be given when blocking cars in the yard. There are both facing sidings and trailing sidings, hence the run-around option in most places. Normally I switch all trailing sidings when I enter a town and then run around and do the facing ones that are now trailing ones. Cabooses are just stashed out of the way, or are occasionally used as a "handle". Two of my industries require switching into a building, no engines allowed.
A a lone operator, I rely on sequencing operations instead of scheduled operations. If I stop and park overnight, I just resume the next day. I will continue to do this when I start using the switching program. I do not utilize a switching yard at the present time. I use the 0-5-0 method of assembling trains in staging. Two of my three staging yards (one double-ended, two stub-ended) are set up with a yard lead and could be used as switching yards, I just haven't taken the time yet to complete the configuration.
That defines my operations in a very large nutshell!