First find a very dense area of buildings that is close to the airport (if one is on the map) because airports convert airport commuters into all other types.

 Next, connect the airport with a station and build your railway line to another station in the densely populated area

 Always buy the train that has the lowest fuel & matinance cost, because it will be cheaper in the long run.

 as you make money, pay back any loans, and then build branch lines

 always build track as straight as possible because the trains travel faster on straits (applies to all tracks in the game)