Cha cha to...?

i'm doing a dancing with the stars kind of thing for my school's senior party. i've never done ballroom before... my partner are doing the cha cha to low by flo rida. i'm wearing a little black, flowy tail dress... do i wear tights or anything? what would i wear UNDER the dress? and what about hair and makeup? it's not going to be a HUGE thing but i'd like to get dressed up a little bit...