Target groups of people who are already doing community service or have majors where they are "community based" such as education or social work. Maybe if your campus has a Neumann Center (Catholic) or other religious orgs...we had Americorps when I was in college (I did both AC and service sorority and events often "counted" for hours for both groups.). I think students who are already involved in helping the community would like the idea of joining an organization that allows them to bond with their sisters (and brothers?) while doing so.
On our campus you werent allowed to do both
ALL GLOs had Chapter on Sunday night at the same time, thus making it impossible.
Good luck!