Important Functions - Unity 4 Game Development - page 598

Start()
The Start() function is called just before any of the Update() methods is called.
Start() is only called once in the lifetime of the behavior. The difference between
Awake() and Start() is that Start() is only called if the script instance is enabled.
This allows you to delay any initialization of code until it is really needed.
The Start() function is called after all Awake() functions on all script instances have
been called. An example of the Start() function is as follows:
// JavaScript user:
private var myLife : int;
function Start() {
myLife = 5;
}
// C# user:
int myLife;
void Start() {
myLife = 5;
}