How do you determine a dragon’s gender?

How do you determine the gender of a dragon, without resorting to asking them? A number of published D&D adventures have dragons in them (natch), clearly identified as male or female. However there is no information on how people know the gender of a dragon. I’m asking about the Forgotten Realms, as the original silver sourcebooks define dragons differently from the D&D 1E Monster Manual. Given the detail dedicated to dragons there should be a gender determination description somewhere.