This trick depends on how intensively you use the game, but it makes it much easier to place your factories and commercial buildings close to where the zoom view is positioned when you start or return to your capital city.
It is best to place all factories together and all commercial buildings together, even if the factories and commercial buildings are not next to each other. The best placement is near the highway and ALWAYS in the capital city, never in the regions.
If the commercial buildings are placed in the regions it is usually complicated to manage them and not very optimized, as you tend to forget to look at them.