When I design and build layouts, I'm disposed toward the small end of the spectrum, and I think a lot about track plans. Operations dictate a big part of what should be included in a plan.
Imagine a simple oval layout; perhaps there are one or two passing sidings, and one or two industry sidings. We also have two sidings representing towns, each with a station/depot and/or a freight house/goods shed. These are the line's two terminii.
A train departs a terminus with the loco at the head end, pointing forward. It travels the loop a few times, then is ready to pull in to the second terminus. In real life, both terminii would include at least a runaround track so the loco could be moved to the other end when going back, and ideally also a turntable or wye so the loco could be facing forward on the return trip.
Runarounds, turntables, and wyes all take up space. They're nice, and they're prototypical, but what if you're building a small layout where space is at a premium, and you don't want to use them? I have three thoughts:
1.) The first is kind of obvious, which is to simply orient the points for both terminii as trailing-point (you can do the same for any industry sidings). This means trains will always travel in the same direction, and will always back into sidings. Simple, but highly unprototypical, and probably a bit boring after a while.
2.) The two terminii points face in different directions, as do the industry sidings. In this case, think about placing your two terminii at or very close to the front of the layout, and think of each as not only a terminus but as visible staging. If you have a kneejerk negative reaction to this, just consider the possiblities. Your train leaves one terminus, switches the trailing-point industries en route, and arrives at a facing-point second terminus. At this point, you can do the runaround and turnaround with your hands, or put a completely new loco on the end, or replace most of the train. It heads back, switching the other industries which are now trailing-point, and arrives home. Repeat ad infinitum.
3.) Include two passing sidings in the oval, and make these your terminii. You can use the passing sidings themselves as runarounds.