How to set shell prompt string

Korn Shell (/bin/ksh)

vi .profile
add following line
PS1="$LOGNAME@`uname -n`$ " ; export PS1

Bash (/bin/bash)
# export PS1="promptstring"

\d : date in Weekday Month Date format
\h : hostname up to first "." i.e. hostname part in FQDN
\H : hostname i.e. FQDN

Description	csh*	ksh	bash	tcsh*	zsh
Current working directory	$CWD	$PWD	\w	%/	%/
Current working directory, with one's home directory by `~'	$CWD:t	$PWD##*/	\W	%~	%~
Full hostname	'uname -n'	'uname -n'	N/A	%M	%M
Hostname up to the first '.'	`hostname -s`	`hostname -s`	\h	%m	%m
Start (stop) boldfacing mode	%B (or %b)	N/A	N/A	%B (or %b)	%B (or %b)
Start (stop) standout mode	%S (or %s)	N/A	N/A	%S (or %s)	%S (or %s)
Start (stop) underline mode	%U (or %u)	N/A	N/A	%U (or %u)	%U (or %u)
User name	`whoami`	`logname`	\u	%n	%n
The shell's tty that the user is logged in on	%l	N/A	N/A	%\|	%\|
The current history number	%h	N/A	\!	%h (or %!)	%h (or %!)
Name of the shell	N/A	N/A	\s	N/A	N/A
Time of day in 12-hour hh:mm AM/PM	%t	N/A	\@	%t (or %@)	%t (or %@)
Time of day in 24-hour hh:mm	%T	N/A	\A	%T	%T
Time of day in 12-hour with seconds hh:mm:ss AM/PM	%p	N/A	\T	%p	N/A
Time of day in 24-hour with seconds hh:mm:nn	%P	N/A	\t	%P	%*
The day in 'dd' format	%D	N/A	N/A	%D	N/A
The month in 'Mon' format	%w	N/A	N/A	%w	N/A
The month in 'mm' format	%W	N/A	N/A	%W	N/A
The year in 'yy' format	%y	N/A	N/A	%y	N/A
The year in 'yyyy' format	%Y	N/A	N/A	%Y	N/A
The date in "Weekday Month Date" format	N/A	N/A	\d	N/A	N/A
The date in day-dd format	N/A	N/A	N/A	N/A	%w
The date in Mon/dd/yy format	N/A	N/A	N/A	N/A	%W
The date in yy-mm-dd format	N/A	N/A	N/A	N/A	%D
The weekday in 'Day' format	%d	N/A	N/A	%d	N/A
Description	csh*	ksh	bash	tcsh*	zsh

References

[1] http://www.thegeekstuff.com/2008/09/bash-shell-ps1-10-examples-to-make-your-linux-prompt-like-angelina-jolie/