What do I have to clean up?

Currently I am cleaning up events after I finish using them. For example…

addEventListener(Event.ENTER_FRAME, contRefresh);

…after using it I do the following…

removeEventListener(Event.ENTER_FRAME, contRefresh);

If I don’t do this it seems to be continuously doing wasting my CPU…

Now for the questions…

(Question 1) if I have a movieclip A which has a child movieclip B, if I remove A does this automatically remove B too from memory?

(Question 2) I’m still learning actionscript 3.0 and would like to know what other stuff I have to clean up (examples please!).