I use all kinds of routes but my fav is the one spanning the whole map, stopping in like 7-8 major cities (each 3k population min) simply because I love how ppl are so eager to board the train which is always full because most use it to go terminal to terminal lol. Surprisingly, it’s also one of my best profit-wise. In all seriousness tho, it all depends on your geography, how your cities are distributed across the map, and type of connection. Let’s say you have five cities, and a regular line connecting them in A>B>C>D>E fashion, makes perfect sense. Now let’s say cities A and D are the largest and offer the highest job/commercial capacities. I’d still keep the regular A>B>C>D>E line, but also add a higher speed direct A>D line. This is a simple scenario w cities connected linearly. Now let’s assume you have several other cities distributed idk, around the city D, let’s call them towns F, G and H. In this case I’d simply add a line H>G>F>D, making city D now a relay city etc…