Hi @hmattoo,
I found this one a while ago:
Another good resource now is actually the SimScale documentation, they were revamped since my post for hex dominant meshing with images of the mesh as a result of changing the settings.
The best way to get use to it is practice a little, I find it a lot better than automatic at the moment. You will be most interested in mesh layers and refinements on individual surfaces for your projects so that would be a good place to start. As well a volume refinements. And of course if you need more help when you do the project just start a forum post 
Kind regards,
Darren