The best practice is to just stay offline when using mods anyway.
More than this though players should not use mods that give them an unfair advantage over players anyway just to be polite. Players should keep in mind that installing mods is technically against the user agreement for Dark Souls 3, and they can technically be banned from online servers if mods are detected in their game while online. In the past this made modding the game fairly difficult, but thanks to significant work by the community it is now easier than ever to add mods to the game. From Software does not officially support modding for Dark Souls 3, and are actually very much against the concept.
