When you go abroad you should know where the closest US embassy is and write down their number and address. Especially when you travel within Europe you should write these things down. Every time we traveled outside of Austria we would write down the number, and address to the nearest US consulate.
When you get to Austria you need to register to live in the country with the register. You will go to the town hall and bring your passport and a registration paper that your host family or dorm director has signed saying that you live at "x" address. You will need to carry this notarized registration paper around with you once you live there. You should get it done as quick as possible once you arrive. You can get the form from the town hall. Once you fill it out and have your housing person sign it bring it in with your passport and they will sign it and give you a copy. :) When you leave you will also need deregister saying that you are leaving the country.
Before you leave you should register with the US government to let them know that you are abroad and where you are. This way if there is an emergency they know that they have an American Citizen that they need to help, plus you get warnings about if there are crisis' or hazards in the countries you register for updates with. It will make mom and dad a little more willing to let you out of the country. ;)
You can register here https://travelregistration.state.gov/ibrs/ui/
It is good idea to update the registry every time you travel somewhere.
Also good country information is found here about traveling abroad as an American. http://travel.state.gov/travel/travel_1744.html.