In case you haven't noticed, there are a lot of people in Test. This means that communications in the middle of an operation are crucial. If you are not in a fleet, feel free to hang out and talk all you want in the Bacon Bar, just don't go into one of the Fleet channels and start talking over other people.
We all know being in a fleet for a long time trying to find some pew-pew can be boring, everyone just needs to understand when talking is appropriate and when it isn't.
If you've already joined and fleet and the FC has assigned a channel, jump right in.
DO NOT SOLICIT INVITES BY JOINING FLEET CHANNELS AT RANDOM. This is a excellent way to have one pissed-off FC when you start talking in the middle of a primary call.
Some simple rules to follow while in a Fleet Channel:
Use some common sense and you will be fine. If other people are chatting it up, feel free, just keep an eye on your overlay to see if the FC starts talking so you'll know to pipe down.
For fleet actions, read up on Fleet Operations Basics if you're not sure whats going on. If you are completely new to any fleet actions then just keep quiet and listen and you'll learn how things operate quickly.