1. Click on "Tools" -> "Message Filters"
2. Click on "New"
3. At Filter name, enter "CLUG-tech" (or chat or announce)
This will make it easy for you to find the rule when you have many filters.
4. You'll see three drop-down menus in the top box. By default, the first one says 'subject'. Click on it, and change it to "To or cc".
5. In the third field, enter email@example.com (or clug-announce or clug-tech, depending on list)
6. In the bottom box, select "Move to folder"
7. Click on "New Folder" to create a folder to store all the messages in. If you're using IMAP, you might have to store this on a local folder.
8. Click on OK. When you receive mail that was sent to firstname.lastname@example.org, it will now be filtered into the folder.
Cc field won't have clug-chat in it when it was sent to the list - i.e.
The most reliable and "correct" method of catching mailing list email is with the
List-* headers. I.e.
List-Id: "Discussions, Chats and Trivia" <clug-chat.clug.org.za>
To see all these headers go View->Message Source