I try to default to "hey folks" or "hey all" unless it's all male "hey guys" or female "hey girls" or friends for sure "hey (words I don't normally use in public)".

I also try to stick with "person", "someone", singular they, whatever is as flexible as possible until I know what the person prefers to be called.

I do find myself accidentally defaulting to assuming he/she depending on the context. Been trying to correct myself so I don't make people feel unwelcome though. :)