Read
Section 2.3 of the APT Howto and learn the secret of netselect.
The best thing about netselect is that it makes lovely, fully formed sources.list's out of thin air. No muss, no fuss, no attempting to suss out just what the h*ll RMS is going on about.
HTH,
Ab.
p.s. The
APT HOWTO is one of the better written and more approachable Debian manuals. Highly recommended. Gets a bit obtuse from time to time, but much less than most.