Writing a Friend's Sorority Rec?

i have a question for the sorority women:

i will be a sophomore this fall, and this winter will be my first rush as an active member of my house. so, i have never really experienced rush from an insider's point of view.

i would like to write a recommendation/letter of reference for a girl from my hometown. i knew her casually, as we went to the same high school and were cheerleaders together for a couple of years. i downloaded my sorority's rec form, but i'm wondering,

what sort of information, in a rec, is most helpful to the chapter at the rushee's college? how much to people usually write about the girl? i have never written someone's rec before, and i guess i'm just looking for whatever insight you can offer.

Thanks a Lot!!