How to Knock-in a Cricket Bat
This first video link is very brief and to the point.
The next 2 video links are in-depth and definitely worth watching. Part 1 is the selection of a good bat mallet and part 2 is the instruction on how best to 'knock-in'.
How to Oil a Cricket Bat
How to Apply Extratec Bat Facing Film
How to Fit a Cricket Bat Grip