Default-virtual server?

I am new to apache 2.0.40 running on Linux and although I have it working I
am unsure what should be done with the default server when configuring 2 IP
based hosts.

Example configurations for my 2 sites:

1. One IP as default server, one as virtual

or

2. One IP as virtual, 2nd IP as virtual, with one of the virtuals sharing
the default server address.

Which one is correct? It seems to work in both configurations but I am not
sure
which way it is best. I also will be putting Frontpage extensions on these
sites if that means anything.

Should I even be using the default server or just use the virtual hosts? If
that is the case how do you turn off the default server?

--thx.

Mike