In this short video, Trevor Corson—the author of The Story of Sushi—explains why you shouldn't mix wasabi into soy sauce and how to season sashimi without overpowering the flavor of raw fish.
[youtube]https://www.youtube.com/watch?v=g-fYp_N9kX4
If that's not enough, he explains some of the finer details, such as the angle at which to tilt your head when eating nigiri, here.