When do Script Components get added to a Game Object?

I have a script attached to one game object that grabs a script on another game object:

function Start() {
	_healthScript = _healthMeter.GetComponent( "HealthScript" ) as HealthScript;

This doesn’t manage to grab the HealthScript from the game object for this particular object but works for others. If I add the following Update() it is able to grab it.

function Update () {
	if( _healthScript == null ) {
		_healthScript = _healthMeter.GetComponent( "HealthScript" ) 
                    as HealthScript;

So it looks like it’s a problem with the order in which the Start() runs as compared to when components get attached. Is there a better way to grab a script off a game object? Is there a different function that executes always after all the game objects have added their components?

Thanks for your help,

It’s a classical issue that the developer doesn’t know strictly beforehand in which order the gameobjects get instantiated and ‘completed’ so to speak. Your problem’s an ancient one, thankfully, and Unity offered a mechanism that solves it a few versions ago: The script execution order.

I recommend you take a look, first of all at this link, which explains the order of event functions within the individual scripts:

Secondly, at this link, which explains what the Script Execution Order feature is and how to use it: