The shotgun seen several times is a double barrel. The sound heard is that of a pump-action gun having a shell racked.
During the opening credits, the girl drives from Tower Records (on Sunset Blvd in West Hollywood), then picks her friend up from UCLA (in Westwood), then drives back to Hollywood. As she passes the Beverly Hills Hotel, she is driving headed west. But, to make such a journey would have her headed east.
Multiple times over the course of the film, the boom mic will dip in and out of the frame.