I learned an entire career's worth of technique in my five years with CBS Promo. Under the legendary Ron Scalera, I absorbed the editorial maxim that I still live by: Clarity is king. Promo is its own beast entirely, and it's harder than it looks to make a simple spot work.
One thing I learned how to excel at is using music, both picking the right song for a spot, and also how to edit it in. The Grammy's spot and the Movies Rock spot each use 8 separate music cutes in a :30 without getting overwhelming.
The Big Brother "Pity Party" spot is one of my favorite copy runs ever. I still can't believe it was approved and actually aired.