what is the best place to add children inside a flex component. which method should be overirired ?
It's best to create your UI in MXML, then you don't have to worry about this, but if you have a dynamic app where you are adding components perhaps based on user action, it depends on what should trigger the add. At least all dependent data should be available.
Override the createChildren() function.
Also, commitProperties() and updateDisplayList() may prove helpful.
I hope that helps.