My best advice is to speak from your ~heart~.
Think about the reason you decided to Rush/Pledge. What has happened since then? How have your sisters impacted your life? What does your GLO mean to you? Tell a little personal story about something special that someone in your GLO did for you. Talk about the benefits of Greek Life and how it could impact their life. But the best way is to show the graduates through your experiences. Be honest, happy, and confident. I'm sure you'll represent Greeks in a great way! Good luck
and let us know how it went.