Do schools prefer kinds of volunteer groups over others?

I need to join one asap..habitat for humanity, charity, ethnic, church, big brother, sexual orientation, etc?  Or do they look more at your role within said organizations?   Thanks

Your role as well as your motivation for being involved in a volunteer group are both important. For instance, if the group has a mission that is in line with your personal goals, your involvement will be easier to discuss in interviews and essays. But keep in mind that adcom is aware that many people try to load up on extracurriculars just before applying to b-school and they can see through that strategy.

Just become involved in something you are passionate about. You will come across as more credible about the cause (vs. clearly just helping out at the homeless shelter 3 months before applying to b-school), you will feel better because you know you're not just doing it for b-school, and you will have much more fun during your activities.

And it doesn't have to be volunteering. Any hobby or interest is fine too (e.g. sports, arts, film, etc.). In fact, if I was the AdCom, I'd even become bored with the majority of applicants listing the same volunteering activities (as noble as it is). An exotic hobby or interest will grasp their attention and even help you differentiate yourself more.