Here is a list of things that you will have to do once you reach Austria.
Inform the respective organization on your arrival like DAAD.
Visit the Stadhaus office. You need to fillup the Residence Registration Form (Anmeldung) and submit it to the Stadhaus. This registration has to be done in the first three days of your arrival in Bonn.
Open a bank account. Find a bank which is either close to your home or to your university. Also ask for a bank clerk who is good at english since you may have to discuss different things with your bank cleark.
Meet your advisor or University concerned person. You need to inform him/her of your arrival.
Go to your University and complete your registration process.
Buy some groceries and do some basic shopping. Make yourself administratively strong. It is important that you start your cooking activities as soon as possible or atleast make the arrangment for your meals. Otherwise you will start loosing weight and feel weak.
There is no need to start your studies in the first week. Take it easy. It is important that you should first settle down. The advisors are very considerate and they do not expect that you will start working immediately. If however, you will try to be extra efficient then your advisor may also give you assignments immediately.
Develop the habbit of writing down the important details. Write down the important bus stops, bus numbers, tram numbers, addresses, telephone numbers etc. Do NOT rely on your memory alone.
Grab a map for your city. Move around in the city and try to understand the routes of buses and trams. Find out the places where you can buy desi things and can have a meal.