Правила на рус. http://codex.wordpress.org/%D0%9D%D0%B0%D0%BF%D0%B8%D1%81%D0%B0%D0%BD%D0%B8%D0%B5_%D0%BF%D0%BB%D0%B0%D0%B3%D0%B8%D0%BD%D0%B0
или http://codex.wordpress.org/Writing_a_Plugin