Be freaking prepared.
But really, the woman I met with at the immigration office today to discuss extending my visa so that I have enough time to take my German language exam and get my residence permit was very pleasant once she realized that I came prepared. She asked for my passport and a copy of it, proof of income and my admission letter from the university, and I made sure to speak in German as well as I could. I was granted an additional 3 months and now I am back to studying.
She also gave me an official list of everything I will need for my residence permit, which I thankfully already have minus my university registration. I get that once I pass the exam.
Dress: Madewell (similar)
Boots: Urban Outfitters
Scarf: Urban Outfitters
Bag: The Noble Collection
Ring: Rebecca Minkoff
Your immigration office may also ask for proof that you have taken a language course, your birth certificate and health insurance. I also paid a 20 Euro fee. Stay calm, be polite and make sure you have copies of everything.