I think you are on the right track with not telling the world every chance you get. I also do not think there is really a prescribed norm for it. The suggested viewing of the WHM and CON quest lines is a good start. What also might be helpful is viewing or reviewing some of the Gridania related quest stuff us. I know that in the Main Scenario start for Gridania there is a point where an Elemental shows up and most people don't understand it. It just makes various noises at them. Also, I'd check some of the material as far as the Echo is concerned. I know that having it conveys an understanding of various languages and forms of communication. Moogles go over this at one point in a Grid quest, I think. There is a thing made about how the character can understand what the Moogles are saying. Your character may or may not have the Echo, that is entirely up to you as a player, but looking at some of the Echo materials out there on it might give you a good idea as to what it is like to understand something that no one else around you does. Failing that, there is the old stand by of looking like your crazy and talking to yourself when you are really talking to an elemental. I am admittedly not sure if Elementals are not visible to everyone when they are manifested. I do know that you cannot see then when they are inhabiting nature things. My understanding is also that they can still be heard by those that communicate with them when they are being a tree or what have you. Hope this helps.
