Thanks to Keith O. for this one...
If you occasionally use the terminal as root, you should consider using a different prompt when 'rooted' - this will help you remember that you are working as root, and hopefully prevent you from doing something that you didn't intend to do.
The first step is to create a file named .tcshrc in /var/root (this file could also probably be created as /var/root/Library/init/tcsh/rc.mine, but I haven't tried that). You'll be placing your prompt in this file, so that it gets loaded each time you start a root session. Here's what Keith O. placed in his root .tcshrc file:
set prompt="%{\033[32m%}%n @ %/ on $host %#%{\033[30m%} "This changes the content and color of the prompt, so that it differs from that of his normal user. If that looks completely foreign to you, that's perfectly normal! Read this hint for a general overview of prompt variables, including an explanation of the color codes, which should help clear things up (a little!).
set prompt="%{\033[0;1;32m%}[%{\033[36m%}%t %n%{\033[32m%}%{\033[33m%}[space]
%c3%{\033[32m%}]%{\033[0m%}%# "Note: Replace [space] with the actual space character, and enter on one line; broken for easier display. That prompt string leads to this prompt display:
Mac OS X Hints
http://hints.macworld.com/article.php?story=20010517111143173