Hello!

[Sagittarian]

Don't assume that a female character is a female player. So if you are not sure, talk to them as per their appearances in game. If it's a boy in a female-coated pixellized form, he'll tell you

I second the "talk to them as per their appearance in game" but want to add that not all male characters have a male player either. Nor are all lalafells played by a real-life radish. :P Just remember that the character is not the player and not everyone plays a character that represents their real-life self. You have to actually *gasp* talk to people to get to know them.