How to prepare for Maketo certification?

Best place to start is here: Marketo Certified Expert Preparation Tools.

It has a Preparation Guide and a Practice Exam, this is where I started. If you have access to the University Portal they have great video tutorials and more there, if you don't have that, my best advice is to read Marketo Docs from start to finish - Product Docs - Marketo Docs - Product Docs​. I did both but found the Marketo Docs section the best for learning. I put a around 3-4 week good learning into the exam and passed it first time.

There is a certification prep class in the education section of this portal.  Take that and you should be fine to pass the test.

I cannot recommend enough taking the practice test early on in your preparation process.  This helps identify the areas you need to work on over others, saving a lot of time in the long run. 

There are several threads on this already, so please do a search for more ideas. I wrote a overview:

Preparing for the Marketo Certification Exam -Marketing Rockstar Guides

which should help.

Thanks every one for sharing their knowledge and suggest me to right way to move on.