Linux init scripts
You will have to adjust the scripts to your environment. Download a script, rename it to geoserver and move it to /etc/init.d. Use chmod to make the script executable and test with /etc/init.d/geoserver.
To set different values for environment variables, create a file /etc/default/geoserver and specify your environment.
Example settings in /etc/default/geoserver for your environment:
USER=geoserver
GEOSERVER_DATA_DIR=/home/$USER/data_dir
GEOSERVER_HOME=/home/$USER/geoserver
JAVA_HOME=/usr/lib/jvm/java-6-sun
JAVA_OPTS="-Xms128m -Xmx512m"