A lot of the information about doing this on Mac OS X refers to the NetInfo database and related utilities, but pre-dates changes which came with Leopard.
On Debian - Ubuntu in my case - most of the information refers to nfs-kernel-server for NFS. Unforntunately nfs-kernel-server requires the uid and gid to be the same on both server and client in the general case. While there is information on how to change your OS X uid/gid it is a pain in the neck and gets worse with more systems.
The best resource I found to address these issues securely is on the Ubuntu forums written by Eiríkr, and uses nfs-user-server to map between the client and server uids and gids - instead of nfs-kernel-server. Install nfs-user-server using your favorite package manager and configure it according to Eirikr.