By convention, the base Tomcat directory (e.g. /usr/local/apache-tomcat-5.5.28) is referred to as $CATALINA_HOME. As a convenience, you should create a $CATALINA_HOME environment variable. For UNIX operating systems one typically modifies a startup file like ~/.bash_login to set and export shell variables while Mac users typically set and export environment variables in .bash_profile. For Windows, go to Start -> Control Panel -> System -> Advanced -> Environment Variables and set your Tomcat environment variables via the GUI.
CATALINA_HOME
Set the CATALINA_HOME environment variable to point to the base directory of your Tomcat installation.
Unix/Mac:
export CATALINA_HOME=/opt/tomcat
Windows:
CATALINA_HOME=C:\tomcat
PATH
Add the Tomcat /bin directory to your PATH variable:
Unix/Mac:
export PATH=$PATH:$CATALINA_HOME/bin
Windows:
append string to the end of the Path system variable
;C:\tomcat\bin