The etiquette and standards are pretty loose all things considered and vary from community to community. The RP scene is so large in FF14 that you can find pretty much the perfect community for yourself with minimal effort, though you might need to pop around servers to go to all the events. My best advice is to find an RP FC and to go over to Tumblr and check out events for the FF14 rp scene there. There's an RP calendar that goes out every week and lists the events that are happening on each day, which server, and at what time. Pick an event whose time works for you then just go and observe and see if it's your cup of tea.

Really the only hard and fast rules are these:
-Don't metagame for other people. Fastest way to get people annoyed is to say their character did something without letting them work it out themselves.
-Communicate. Different people have different standards, so you're better off working things out before you even begin.
-If you're going to an event then you should avoid posting a five paragraph essay when replying to people. Chat scroll is murder in this game and you'll likely annoy people if you're in a group of more than 5. One on one it's okay however.