( If you have one interface, then you will only have one choice.
Enable Net-Booting on the interfaces from which you want your clients to make their requests.
( Realize this volume chosen cannot be used as the volume that contains your Macintosh Net-booting Images, since it will need to be a HFS+ based volume and the Mac OS X server will modify the format of the volume it is being installed upon to something different (UFS) than what you format it before installation.)
If this machine will seed the network, make sure you obtain a range to seed from your network administrator. Subnet Mask, Gateway/router, DNS, Time Server (if you have one), NetInfo Server, and determine if this server will be acting as a router and seeding the network for a zone, or another network device will be doing this.
(If you do not wish to buy a copy of Mac OS X, then you may check out Alistair Riddell's web site which offers information on how to make this work without the server software.
I have a page for setting up netbooting with Linux that is rather detailed if you would rather view it instead.
This page was placed here to include some information about making netboot with Mac OS X Server edition. Setting up the Mac OS X Net Boot Server Netbooting Mac Links from Head Page: