Groups (the people kind, not the abstract algebra kind)

School of Doubt posted my question!  To wit, how do I redirect the lamentable tendancy for female students in a lab group to watch/take data while letting the male students do all the setup/building stuff?

I'm just as guilty here as my students.  While a student, I didn't know how to balance myself and my lab partners so that everyone got roughly equal time doing stuff/writing things down.  Now I'm supposed to be the wise teacher, and I still don't know how to do this.  Your experiences or suggestions, gentle readers?