Often by lurking, you can learn a good deal about the unwritten rules of the community. While we should respect the privacy of others, we should also realize that not everyone has our values. While most networked computers have many security features, we should realize that network administrators have access and no security system is foolproof. Therefore, it is important to be careful about what you put on web pages, store on a networked computers, or send via email. To make a long story short, what you don't want public, don't put on a networked computer.
People also tend to get careless with email.
Library and campus labs can have many people waiting to use computers, so if a lab is crowded and people are waiting, avoid playing games, chatting with friends, and aimless surfing of the net. However, if it is your computer or people are not waiting, take time to play. We often learn most through play. In the textual world of chat rooms, email, Moos, Muds, and web pages, using capital letters means that your are shouting and doing so isn't very nice. Try to avoid it.