Pref Night

i have a little question for the sororities. our pref night is coming up really fast and there is this one sorority that i want to join and i want to make sure that they put me high up on their list. i don't know how i can let them know this without coming right out and saying it though. any tips? and there is just one more question i have. is pref always at night? i was just wondering because they call it pref night and they told us to be there at 11, but i forgot to ask if it was in the morning or at night. thanks a bunch.