I have put down the exact order of things you should follow. You can print out this checklist for yourself and go through it step by step. You will do just fine if you follow this order. If not, things can get messy.
1. Notify your agency / school about your visa result
2. Read all emails from your agency / school
3. Pay your university fees if you haven’t paid yet
4. Send your agency / school a confirmation of payment and make sure to check with them if accommodation & airport pick up is provided
5. Buy / exchange currency to Euro
6. Decide on a travel date & purchase travel insurance
7. Pick up your visa
8. Book your flight
9. Notify agency / school once you have booked your flights
10. Collect all your original documents, and take them with you
11. Start learning German to know basic phrases 12. Learn more about the public transportation system
13. Research in advance about the cultural & geographical differences
14. Make a notarized copy of your passport
15. Fly to Germany
16. Pass the passport control
17. Buy yourself a transport pass
18. Once you have arrived, send an email or a text to your school/agency that you have safely landed and reached your accommodation
19. Respect university rules
20. Enjoy the culture shock
21. Get acquainted with bureaucracy
22. Learn the German post
23. Stay calm