Where to define vhosts

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I am wondering what the proper way to add vhosts to the Apache config.

I've used 3 methods.

1) add them to the bottom of the httpd.conf file
2) add an include at the bottom of the httpd.conf file that includes a 
file containing all the vhosts
3) adding a vhost.conf file to /etc/httpd/config.d/ directory

In the last method, the vhosts are included in the middle of 
/etc/httpd/conf/httpd.conf file.  Is this a problem?

Is there a better method?

Thanks!!

Keith