Practice listening to Spanish-speaking news programs (BBCMundo, Univision, Telemundo, etc.), to radio programs, or online. Listening to music in Spanish is extremely important, but listening to news reports and interviews is what will help you to be successful on the AP exam. Some very good online sites are listed below.
http://www.rtve.es/rne/audio/sr5r.htm (noticias. España)
http://udgtv.com/radioudg/guadalajara/ (Universidad de Guadalajara, Mexico)