Nervouse about starting Ballet!?

I have been thinking about starting Ballet I am 18 and I am a beginner so I decided to wait a lil bit and try doing some home study for a lil bit to see if I could get familiar with ballet and get into better shape so I started doing simple Barre excercises Tendus,Frappes,Grand Battmons exct. now Im like okay I think Im good enough to start a real class so I was wondering what a ballet class is like what should I expect? and also what should I bring and wear like when do you take off your warm ups and such? thanks