If my feeble memory recalls correctly, the trick to being an extra was to stand next to the prettiest girl and try to pick her up between takes. Usually she was a drama student at NYU or taking acting lessons...but hope springs eternal.
Watch this, its every 80's film cliche in 6 minutes! (it starts about 10 seconds into the clip.
http://www.youtube.com/watch?v=C37rCtqiIKs&search=80s