Played TTD along time ago (but then I used 1 line for 1 train

But now I am more learning from the signal stuff (and that's working), however if I see some of you have those nice "main" lines. How do you start with such a main line.
Because I start everytime building railroads from coal to powerstation and adding more and more tracks / stations to it. However I get a (working

Also when connecting station, what's the best way to connect a big station, so that I don't get a qeue in front of the station.
Learned A LOT of this site when searching, but couldn't get above questions answered
