Set up your PXE server that will hold the OS images for your client.
Setup the install client image on the PXE server. For Red Hat Linux, this would involve creating a boot media image with a kickstart file, or making the kickstart file available on the PXE server. For SUSE Linux, this would involve creating an installation media image using YaST, and making the image available on the PXE server.
Refer to the Linux vendor's documentation for details on various deployment options:
For Red Hat Enterprise Linux Client, see: http://www.redhat.com/docs/manuals/enterprise/#RHEL5
For SUSE Linux Enterprise Desktop, see: http://www.novell.com/documentation/sled10/#administration