Seems that another round of YKI testi is coming soon. So, I actually feel really motivated to tell you more about preparation process.
Let's start with some must-visit links:
University of Jyväskylä organises test and checks it. And they also share sample tests with you! Lack of motivation? Do tasks in group, for instance, with your friend, regardless whether you are on the same language level or not. I did so to practice listening - was difficult to concentrate on the listening tasks on my own.
Helsingin aikuisopisto has compiled links and videos. Pay a special attention to selkouutiset (news in simple Finnish) - this way you will learn language and keep updated at the same time. Actually, I surfed their pages a bit and it seems that they have online courses - so busy schedule is no excuse for learning language, especially when it comes to writing (based on feedback from my friends, a most difficult part of the exam). Check this course, for example.
YLE learning materials - it is classic! I did only their sanasto exercises. Worth checking to develop your vocabulary, even if you have no YKI plans yet!
Soon I will tell you more about preparing for Kirjoittaminen part. Stay updated!