It is essential to know a bit about the bureaucracy surrounding studying in Turkey as a foreign student. First, you need to apply for a student visa at the consulate in your own country. This can be quite expensive. When you get to Turkey, you need to register with the police and obtain a residence permit. IT IS A VERY GOOD IDEA TO MAKE YOUR APPOINTMENT FOR THIS ON THE INTERNET BEFORE YOU ARRIVE. It is often the case that there is over a month's waiting list which means you won't be able to register within the required time slot. Sometimes the police can refuse to register you or try to get a bribe out of you if you do not register, I have met many people who have had this problem.
The most important thing is to stick to the deadlines given by your home and host university's International Office, they are always really helpful. Most of the information about my host country and my university was online. I would recommend you do some research before leaving so you can think about where you want to live (town, campus etc) and to get an idea of what life is like in the foreign country. That often helps to overcome the first big culture shock. Also check the weather forecast and the average temperatures for the whole year, this will help you pack the right clothing because South does not automatically mean hot all year. Istanbul for example gets very cold and windy in winter. I also highly recommend the Intensive Language courses they help you to find your way around more easily and integrate better.