I've been here in Germany for well over a year now (but not quite a year and a half yet). Besides the usual of finding a German course or looking for an apartment, here are some other things that I've figured out along the way so far...
As soon as you settle in, you will find yourself needing one of these again. Find a tandem partner as a start, talk to people in your German course, look on a website like Toytowngermany.com and find yourself an interest group or event going on that interests you and go. Just go. It will fight off the feeling of loneliness or uselessness you might get when being away from home (wherever or whomever that may be for you).
2. Allow yourself to go nuts.
Not off the deep end nuts, or even with your credit card nuts, what I mean is that from my own experience, life can be frustrating in another country sometimes, allow yourself to get pissed off or annoyed. Get upset, figure out why you are upset (you may be surprised that its not quite the most obvious reason). Then pull yourself together and try not to hate Germany for it. A good mantra: Different doesn't mean wrong.
3. Find a go-to guide
Either in the form of a book, a forum or even better a live person, find someone who has "been there, done that" and preferably speaks German well to help you out. You will need help. If not in language, then figuring out how things work (or how to fix them when they don't.)
4. Visit home.
It will put things in perspective for you, whether in a positive way (you might be glad you can go back to Germany after the visit), negative way (you might realize that you don't want to be in Germany forever) or in a neutral way (no place is perfect). In any case, get yourself out of Germany after a while and give yourself a chance to revamp.
Surely others who have been abroad longer have more to add to this list... feel free to share.