Do the practice exams from past years, but also do extra reading and listening if you can!
German radio stations:
http://www.listenlive.eu/germany.htmlListen actively. Don't just have it on in the background and forget about it, but actually try to understand what's going on. Don't worry if you can't understand most of it - you're not supposed to be able to. But it is good practice to get your ear attuned to the sound, rhythm, tone of Deutsch.
Read, read, read:
Der Spiegel:
http://www.spiegel.de/Das Journal:
http://www.dasjournal.net/Two of the most highly regarded newspapers in Deutschland. Good for learning some new vocabulary, or even just to see how all that boring grammar you've learned in class actually gets put to practice. See if you can spot uses of subjunctive, passive, plusquamperfekt (I don't know how to say that in English, LOL
)