I've read the apt-get tips, but still am on not clear on what is correct to have in the sources.list file, and the apt.conf file.

After a 3.4ct HD install the sources.list file, lists stable, testing, unstable and experimental sources. Is that the best setup or should we comment out some?

Also, in apt.conf it lists the default release as testing, how is that setting used?

Example: If a do a apt-get install XXXX, will it use testing as the default source since its in the apt.conf file?