Last week, I was able to become Professional Scrum Master. Can you believe that? :)
I knew some things about Scrum for some time now, but I've never attended real Scrum course until about a week ago. The course took 2-days to complete and was conducted by one of the local training centers. After the course I was given password to complete Professional Scrum Master I assessment from Scrum.org.
Except for taking Scrum training, to pass the assessment I believe you clearly need to take "Open assessment" (which is free of charge and which you can find on the same website) as many times as you need to be comfortable with passing it. The real assessment contains 80 questions while you have only 60 minutes to answer. And difficulty of number of questions is significantly higher than questions from "open" assessment. To pass the exam, you need to achieve score of at least 85%. Personally, I thought that I passed comfortably, but it turned out that I got "just" 89%.
After passing it, you need to wait for a few hours before your certificate is ready to be printed from pdf document :) Oh, and you are given the right to use the badge: