We all know how difficult it is to identify the sex of these fish, so please post a picture in here and we'll try to help you (or at least give an educated guess!).
This is the quickly method for male&female undestanding
You should catch the fish, and look at the thorns
This is female
Male
Its good method for young fish which you grew from fry.
But it does not always work with wild caught fish, because wild caught females also may have big thorns.