Judgement in all things. I generally assume that everyone can guess anyway - which cleverly removes the issue of freaking out if people know - and use my judgement on whether or not to tell people. I've only had one guy be a twonk about it, and that was when I wasn't present and he was being a privileged ass hole. On the rare occasions people read me as trans rather than cis, I'm generally laid back and matter of fact about it so it's not really an issue.
I will say that being open is a very powerful thing, but you are under no obligation to live visibly.