On philanthropy day, I would try to find out what the national and local philanthropies are (some groups have a local one in addition to national...). Try to find out how often they actually do service projects and what kinds of things they do (i.e.: Halloween party for kids at school for the deaf, fun runs, etc.). Also, try to get to know the girls you talk to and just make a friend! Find out what kinds of fun things they do like formals, sisterhood events, etc. Maybe ask what the new member program is like. You don't have to talk about anything too serious on that day. Just try to find out more about the girls and their chapter, what sets them apart. It will help you get a feel for the different chapters.
How exciting for you! Remember to just have fun! This is an awesome time that you will never forget, no matter where you end up
