Honest question, what do they prefer to be known as?

For example, if there is a person called "pat" who prefers to identify as neither male nor female, do they prefer to be called "them" in the third person? Or do they prefer something like "hir" or "zee"? (which are alternate forms as far as I have heard).

I think that if this is a hard problem, it should be solved immediately, without resorting to arbitrary made-up conventions, like using "they" everywhere.