Hey
)
Some of the things that I did for the chapter I was Sweetheart for was baking treats weekly for the boys when they got out of chapter meeting, helping clean the house after parties on the weekend, helping with dinners/formal decorations, helping recruit new members during rush (giving house tours, giving information about the fraternity, answering questions, convincing rushees to come to rush events, helping set up.. ect), talking to parents during parent's dinner. I also made gifts for all the new brothers every semester. The girls/sweethearts involved with the house also make lettered shirts for the new brothers each semester.
Basically, learn as much as you can about the ideals and history of the fraternity. Then help out wherever you are needed. ;o) <3