If you can't choose a mirror to use with apt, you can use
netselect-apt downloads the full mirror list from Debian's web site and uses the netselect to choose the fastest one.
netselect is an implementation of "ping", but it is smarter than "ping".
netselect-apt finds the best mirror and writes a sources.list file that can be used with apt. To install this tool:
apt-get install netselect-apt
netselect will also be installed, because netselect-apt depends on it.
You can specify which distribution to use, the default is stable.
You can include non-free section:
You can use ftp mirrors instead of http: