I plan to setup a server for providing shared and VPS web-hosting services.

I was looking for information on what all special customization and configuration I should make for efficient and secured implementation of hosting services ( i.e. any configuration or change I have to make from default settings) :
1. Apache :
a> I have seen, different types of paths are used in different servers :
/var/www/vhost/USERNAME OR
/var/www/USERNAME OR
Any particular reason for such variations ?
b> In some shared hosting servers, I have seen, VirtualHost entries are not mentioned in httpd.conf. Any particular reason ? Any idea how else they can be implemented ?

2. DNS
Any difference between BIND and BIND-CHROOT ? Which is preferred for web-hosting and why ?

3. VSFTP,MYSQL and other servers : Any particular customization I should be aware of ?