Yeah, well, join the club. You're not a freak if you can't come up with an idea right away.
Ideas come from anywhere and everywhere.
Pay attention to your daily life, from reading the Sunday comics to watching your brother smirk at a girl. Movie ideas can come from the books you read, the 'zines you write, or the music you make or listen to. Before you know it, a great idea will smack you in the face. Consult the posse Talk with your friends or family about your movie and listen to their ideas. Allow them to inspire you.