How can I unmount an nfs-mounted partition from the client?

Or is that even the right question?

Here is the situation: I have a directory exported on an nfs server (a desktop PC) and mounted from the command-line on my laptop. The desktop is a dual-boot which spends most of its time in windows (kids gaming machine). My plan is to have somewhere to store backups.

What should I do on the client before shutting-down the server PC to let things end gracefully?

Can I set-up fstab (or ?) on the client so that it will mount the exported drive if it is there but not cause problems if it is not there?

Is there a better way to do this???

Many thanks Syd