At my school all three sororities have formal and informal rush together so it is somewhat structured. In the fall is when we have formal rush. We usually have information night, four nights of events, Preference Night and Bid Day.
In the winter is when we have informal rush. We have information night and Round #1 at school so all of the rushee's can meet the girls. During Round #2 two sororities hold events off campus and the rushee's get to choose which event they want to go to. Round #3 and #4 is the same as #2 but there are two different sororities matched up. Then we have Pref Night and then Bid Day.
Have a nice day