man tcsh
scroll to about 80% down the man page and you'll see a discussion of the various PROMPT tags you can use.
The default is [%m:%c3] %n%# where:
%m = hostname (localhost, in this case)
%c3 = current path (showing up to the last 3 directories)
%n = current username
%# = prompt char (usually > or # if root)
Change the prompt by issuing the command:
set prompt="<new prompt string>"
where <new prompt string> is the format you want to use. For example, if you want the time to be printed at each prompt:
set prompt="[%@] %#"
There's other tricks you can play as well, such as making strings bold, underlined, etc.
The good thing is it's all temporary, so if you really screw up, just close the terminal window and open a new one. When you find a combination you want to keep, add it to your ~/.tcshrc to install it each time you open a new shell.