When you start a new game, then find one of the places on the map, where you can make the largest tunnel and do. When done you will find yourself having many many many millions of dollars on your account.

When your train arrives in the stattio and begins what can be a long loading/unloading process, order it to the nearest train depot. As soon as it's set off, hit the "go to nearest depot" button again and make it skip its orders to the next place on the line. Voila, your loading/unloading time has been minimised.