There are many other fish in the sea.
From my own experience of my first breakup, i noticed i was completely irrational and overly emotional. I thought the break up was the worst thing in the world. There first piece of advice to my friend would be to realize there are many other "fish in the sea." There are many other boys out there that would treat my friend better.

Don;t look at his facebook!
Many girls stalk their ex boyfriends facebook to keep tabs on the people he is talking to. It is the worst idea ever. If two people are broken up, then they can talk to whoever they want. Therefore, stalking the exs facebook will only make the recovery process longer and much harder.