There are multiple methods and tool that can be used to fix a ball mark, but some can actually cause damage to the green and slow the recovery of the ball mark In the videos below Dave Davies explains how to properly repair a ball mark.
Click on the link below to see Dave talk about fixing ball marks.
https://www.youtube.com/watch?v=kx1R_rIoR0g
In this video Dave discusses how to fix deep ball marks.