/etc/rc.local
/etc/init.d/script
Make it executable:
$ sudo chmod 755 /etc/init.d/superscript
Register script to be run at startup:
$ sudo update-rc.d superscript defaults
[[http://raspberrypi.stackexchange.com/questions/8734/execute-script-on-start-up|http://raspberrypi.stackexchange.com/questions/8734/execute-script-on-start-up]]