I would recommend coming up with some rules for play on your server. As much as we hate them they are needed to stop people messing around and spoling the server for everyone. Especially recently there has been a number of "trolls" roaming Simutrans multiplayer to such an extent that Moblet and 50 were forced to restrict players to prevent it.
You might also want to specify the obvious such as what pakset you are using, what version of simutrans, what map settings (JIT2 if nightly?) etc. This can help people decide if they want to play or not as they might not like some map settings.