==== Avoid Code on Buttons / MovieClips ====

Object actions (attaching code to movie clips and buttons) should only be used when absolutely necessary. If used a minimum amount of code should be included and it is recommended that a function call into main action script of the movie should be used.

	onClipEvent(mouseDown)
	{
		_parent.doMouseDown(this);  // call function in parent context
	}

is recommended if object actions are necessary. This redirects all the functionality into the main timeline of the movie clip.

Better is to name every instance of each object, myButton1, myButton2, etc... and to set it's callback function at initialization.

	function init() {
		// ...
		myButton1.onMouseDown = function() { 
			_parent.doMouseDown(this); 
		}; // Initalize the button's callback at runtime.
		// ...
	}

I do this because it's easier to track code if it's totally seperate from graphically objects. Also, object code gets erased if you delete the object from the stage. Ben Schleimer 

It's important to note that this is not only relevant when building anything you might consider a "large" project. If there is a likelihood that anyone else (or even you) will revisit a project at a later stage it will be an extremely valuable move.

If you do this you will also find it easier to transition to AS2.0 and full OOP / OOD flash coding, if you haven't already done so.  Jason Milkins