I recommend to use Proftpd. The procedure is well explained here:
http://www.debian-administration.org/article/Setting_up_an_FTP_server_on_DebianFor cross-reference, use these two sites:
http://www.debianadmin.com/proftpd-server-installation-and-configuration.htmlhttp://www.debianhelp.co.uk/proftp.htm(If you cannot find the configuration file in /etc/proftpd.conf, it will be in /etc/proftpd/proftpd.conf)
Please make sure it contains the following lines:
.....
DefaultRoot ~
IdentLookups off
ServerIdent on "FTP Server ready."
.....
This will jail users to their /home/username directory, as it is usually done when giving users shell access on a *NIX system. If you wish to restrict this to their /www directory, try this line:
DefaultRoot ~/www
By default, anonymous access is switched off.