Sounds effects in animation

Hi ,

I have a very basic yet an interesting question. I have tried to search Google for tutorials on this subject without luck so far. I want to learn the key techniques of mastering the art of adding sound effects to your animation.

Then I have two more questions that need to be answered as far as background music is concerned:

1-Do PROs first create their animation and then try to find the matching score to it?
2-Do PROs first find their music score (background music) first and they keyframe or merge various elements of their animations?

Like if you take a look at any good demo reel you will notice that visuals somehow match with the background music.

I don't know if I have put this up properly but this is what I want to learn.

Cheers


TweenGuy