I am so excited to say I passed the PSM1 with 92% score and I just spent a week for the preparation.
My approach:

1) Read the scrum guide once
2) did practice test on Scrum.org
3) prepared some notes
4) Read the Scrum guid again
5) someone recommended couple of site – thescrumexperts.com and MP paid one
6) revised my notes as I was preparing along

Passed 🙂
I thought some free mock tests are somewhat easier than the real exam so be careful guys.