The first rule should be to call people what they want to be called. My given name has a few nicknames, but I don't like to be called any of them, and introduce myself using my given name. I don't get offended when I am called by another name, unless I have already identified myself and used the name I prefer to be called. I still don't express my displeasure - I just don't answer to that name.
Even though I am a guy who likes to dress up occasionally, I have a female name and show my en femme pic. So I should be referred to as "she". Some members here use a generic or male name, and want to be called "he". Seems simple enough to call people what they want to be called.
But, it gets tricky sometimes. Sissystephanie, for example, has made it clear many times that he is a guy who likes to wear women's clothes and want to be referred to as "he", but uses a female name. That may not be known at first to a newcomer to the forum. Another situation on the forum that may allow for a bending of the rules is a post in response to crossdressing/marital issues. For clarity, it may be best to refer to "he" and "she" even though the "he" is a CD with a feminine identity, female name and pic.