A preferred way to execute a script during boot is to create an Upstart job. Job configuration file might go to /etc/init (system jobs) or to ~/.init (user jobs).

Upstart is an event-based replacement for the venerable System-V init introduced for the first time in Ubuntu 6.10.

You will find answers to basic questions here.

To get started go here.

Detailed documentation having zilion examples can be found here.