I would maybe suggest you start out by having a browse through these
threads (well, the ones that look like they'd be helpful to you, anyway).
General tips or advice I could give you:
1. Make sure to dive in and get integrated with the Germans. Sometimes it's easy to find other English speakers and spend most of your time with them, but you're not really doing yourself any favors. Take advantage of the time here to really learn the language and culture.
2. Cologne is a really fun city. It's decent for shopping and the people have always seemed pretty happy-go-lucky to me in comparison with many other parts of Germany. Get out there and drink some Kölsch, support the hockey team, etc. Unfortunately you'll have missed Karneval this year.

3. If there are any over the counter medications you feel you couldn't survive a year without, stock up on them now. They'll have Vick's cold medicine here- but beyond that...
4. Travel. Go to Aachen, go to Holland, get up to the North Sea.