How to not derail your train?
If you don’t know the track you’re driving on, drive with caution. Take corners slowly. Sharp ones should be taken at 20km/h max. On more straight parts, you can try speeding up a bit, but do not rush. Keep your eye on the speedometer and brake or accelerate if necessary. Distraction might lead to a derailment.
If a switch is coming up, slow down. A switch that turns off the track (either a \ or / showing) is too sharp to take at high speeds. 20km/h is suggested.
Pay attention to the map, as the map allows you to see the upcoming corners. That way, you know what the track might look like ahead of time, so you can brake if necessary.
When driving at a station (unless passing through), you should slow down to 20km/h. Nearly every turn can be taken at this speed and it’s also easier to stop if something does go wrong.
If a vehicle is close to getting derailed, you might hear the wheels grind against the track. This means you must slow down.
When driving with cars, you might have a harder time stopping, so be sure to brake hard enough in corners and be aware of hills. If inclines are approached with too low a speed, you might get stuck on the incline. If the track is going down, brake. Not braking hard enough might result in the train going too fast for an upcoming turn, so keep your eyes on the speedometer.
You might have the hang of slow driving now, but you probably want to speed up.
Make sure that you speed up when the whole train is out of the corner. Your locomotive might have made it out of the corner, but if the rest of the train is still in the bend and you accelerate, your cars will take the turn too fast and derail.
While driving at speed, make sure the cars don’t derail. Look backwards to check up on them regularly.
If you don’t trust that a corner is safe enough to take at speed, slow down. Remember; it’s not a race.
Once you know the track a little bit, you can try driving over said track at faster speeds. Try to take that track with an increment of ~5km/h once you’re certain you can take it at that speed. As mentioned before, if you hear the wheels grinding against the track, you might want to slow down.
That was it! I usually write things in a very short manner, so if it wasn’t clear, feel free to ask questions. Also, if you have any criticism on the guide, whether positive or negative, do tell me! I’ll edit it if necessary.