about anonymous, it's quite simple.
add : anon_root=/var/ftp
for other users, depends if you're working in the virtual users way.
if you're not, you can use chroot_local_user=YES to root them in their home directory. this is dangerous.
you better use local_root=... to root them to a specific directory. of course they will all be root'ed to the same dir.
you can use user_config_dir=... to specify different options such as local_root for every users.
but my best advice is to visit http://vsftpd.beasts.org/vsftpd_conf.html