There are 2 things I found out about on the first day:

1. Electric Adapters - never forget them
2. Never hesitate to put your baggage in a locker on the Bahn,
   (no matter how sure are you that "I'll be in the apartment any minute now")

My first day was mostly me walking with 2 Tons of baggage on my back in Warschauer Straße.
It was less than ideal at first, but after eating some Pizza&Beer everything was better:

After that I finally settled into the Apartment, slept through the night..
Only to find out that I don't have the right Adapter for the outlet in Germany (or any Adapter at all)..