I've been seeing this "Sushi Etiquette" poster pop up all over the place lately (see this google image search):
I've posted it small here because before you read it you need to know something:
This is a guide on how to be nervous and not enjoy your food.
It contains mostly ignorable advice with the exception of someone who wants to marry the emperor's daughter, or more likely, someone who likes to tell other people why they're wrong about how their eating.
Sure, its funny, and there are a few thing in here that people will say is spot on. But as the comments on this randomly selected blog post show, nobody really agrees what right and what isn't.
If there one rule you can believe, its probably the first; use your hands or chopsticks. I saw a guy use a knife and fork once and they looked like a total bonehead.