Thanks for the bump, alphaalpha. This thread has been so helpful! My colony has 18 sisters (compared to 45 or so that the two NPC chapters on my campus have), and I really appreciate all these great ideas (now I really want to have an NPC social!).
It is important not to make recruitment your only goal. Be very active in outside groups, hold philanthropy events (including some on campus), and have a lot of mixers (with fraternities, sororities, and other campus groups) as well as sisterhood parties (going out for pizza or whatnot). As KKC said, "If you build it, they will come" - I believe that too! If you show PNMs that you are as active as GLOs with even more members - what dedication! Many girls would love to join an organization like that.
Please continue to share your ideas. Thanks!
Much love, Marly