I've added a video that I produced last year outlining theory and practice around warmup to the Resources section of the MCC coaches page.
I feel pretty strongly about the importance of a proper warmup within the overall training session structure. It provides an opportunity to address all of the elements of player development - technical, tactical, physical, and psychosocial - and sets the tone for our culture and the session activities that will follow.
Here is a direct link to the video: