There is a ceremony, written by our Zeta Xi chapter at the University of Alabama in Birmingham.
You can find it by going to the myDG section of
www.deltagamma.org. You'll need to know your member number in order to access that section of the Web site. Look under Collegiate Resource Center and then, under that, click on Rituals. It's found as a .pdf.
As for criteria...I think it's mothers of initiated members, but don't know for sure. Seems like I've heard of it being given to a beloved housemother. Maybe someone else can chime in?