• as much as is possible, put all code in classes
• avoid the temptation to place non-trivial code on frames, clips, and buttons
• if you want to put code on something, that's a sign that it needs to be integrated into your application's architecture
• keep each class in a separate .as file
• in your movie, use #include to load each class
• remember, a class is just:
  • a bunch of properties
  • a bunch of methods
  • a constructor
• keep the above items separate! as follows:
  • assign all instance properties to YourClass.prototype
  • assign all instance methods to YourClass.prototype.
  • assign all static class properties to YourClass.
  • assign all static class methods to YourClass.
  • in the constructor, ONLY do initialization -- don't put any other code there
• for example, here's the stripped down source for a MessageDialog class

// CLASS MessageDialog EXTENDS MovieClip
MessageDialog = function () {
}

// SET SUPERCLASS
MessageDialog.prototype = new MovieClip();

// PROPERTIES
  MessageDialog.prototype.msg_txt = null;
  MessageDialog.prototype.title_txt = null;
  MessageDialog.prototype.titleBar_mc = null;
  MessageDialog.prototype.ok_btn;
  MessageDialog.prototype.close_btn;

// METHODS
  MessageDialog.prototype.init = function (title, message, x, y) {
  }

  MessageDialog.prototype.dragDialog = function () {
  }

  MessageDialog.prototype.dropDialog = function () {
  }

  MessageDialog.prototype.closeDialog = function () {
  }