Over the past years, the Internet has become accessible to a broad public. Unfortunately, together with that accessibility, along came a lax attitude due to people unfamiliar with the (non-binding) rules from the older Internet.
On this page I have collected some links that describe good behaviour on the net. Most of them are about email and usenet; they are what I use most. Besides, it is also there that your behaviour may be most intrusive towards other people (except maybe for IRC, but there you have operators to interfere when things become excessive). Note: some of these links are not in English.
Hoe te quoten in Usenet http://www.houghi.org/quote/
What is Quoting? http://home.online.no/~vidaandr/news/FAQquoting.html
E-Mail Etiquette http://www.iwillfollow.com/email.htm
Message Editing and Quoting Guide (with Examples) http://www.math.fu-berlin.de/~guckes/mail/edit.html .