If you want a stations with fluent traffic, keep those 2 basic rules in your head:
1) In a station one track per line.
2) Only build so many switches as you need.
And before you connect a city to your network, look around it, if there are other cities, which you may want to connect later on and what the contourlines are showing, what the terrain is like.
Example: You want to connect City A to your network. There are also the neighboring cities B, C, D and E.
D and E are blocked off by mountain ranges so you decide, that you want to connect A to your network by extending your mainline and that you want to connect B and C to A, each by a seperate line.
So in the end you will have 3 lines in planned station on A, so it will need 3 tracks => 3-Track-Passenger station.
This way, you’ll save money, because otherwise you may have only build a single-track station and later on, when you want to connect B and C, you would’ve to tear down the station, maybe connecting tracks and rebuilding it, so investing unnecessary sums of money.