Put this file in /etc/init.d/ and edit {THING-TO-LAUNCH} as appropriate. You can run `sudo update-rc.d {THIS-FILE'S-NAME} defaults` to `start` at boot and `stop` at shutdown.

launch script

#! /bin/sh
# /etc/init.d/{THING-TO-LAUNCH}

### BEGIN INIT INFO
# Provides:          {THING-TO-LAUNCH}
# Required-Start:    $remote_fs $syslog
# Required-Stop:     $remote_fs $syslog
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: Simple script to start a program at boot
# Description:       Simple, conventional, practical launch script. By Andrew Monks.
### END INIT INFO

# run `sudo update-rc.d {THIS-FILE'S-NAME} defaults` to `start` at boot and `stop` at shutdown.

# Carry out specific functions when asked to by the system
case "$1" in
  start)
    echo "Starting {THING-TO-LAUNCH}"
    # run application you want to start
    # runs as root by default, hence the `su`
    # /usr/bin/{THING-TO-LAUNCH} # on its own works if you'd like to run as root.
    su pi -c '/usr/bin/{THING-TO-LAUNCH}' # or whatever
    ;;
  stop)
    echo "Stopping {THING-TO-LAUNCH}"
    # kill application you want to stop
    su pi -c 'killall {THING-TO-LAUNCH}' # or whatever
    ;;
  *)
    echo "Usage: /etc/init.d/{THING-TO-LAUNCH} {start|stop}"
    exit 1
    ;;
esac

exit 0