I have spent some time observing rugby fans in their natural viewing environment, and have compiled some simple rules to streamline your Rugby World Cup viewing experience.
1. Watch the game. Don't try and do anything else at the same time (including conversation).
Multi-tasking is not welcome here. If you are not giving "constructive feedback", remain silent.
3. In the event of something bad happening (again, a relative term), you can either do the "fist shake" (one hand raised in a fist, preferably with a drink in hand), or the "goal posts" (stand up with both hands raised). Be incredulous.
4. The referee relies on your feedback, so it is important to let him know exactly what you think of him, especially when he has done something wrong (see rule #3).
5. Be literal in your verbal feedback. Verbs are highly recommended.
6. Don't be too literal in your verbal feedback. Non-specific comments are not appreciated (refer back to rule #1).
Now just sit back, relax, and enjoy your rugby viewing experience!