tar - restore a file

We use tar for backing up a server.

I need to restore just one file from this backup.
Anyone know the syntax?

I need to extract a file and place in a different directory on the server as I do not wish to overwrite the current file..

Check your man pages for your version of OS (since you did not post it)

You can try after checking how it was listed in the tar (see below)
# cd /tmp
# tar -xf /dev/rmt/0n ./mydir/myfile

You must see how your file was backed up - if it's ./mydir/myfile then you can put it in a new directory (all the mydir directories above it will be created under whichever directory you are in).
If it's listed as /mydir/myfile, then it's going to restore the file in the original directory - so you must do the restore on a different system to avoid overwriting the file. Use the tar -tvf /dev/rmt/0n to view what is on the tape (change /dev/rmt/0n to what ever your tape drive is)