BELIEVE your friend.
LISTEN without judging.
TELL them you care.
FOLLOW your friend's lead. Support his/her decisions.
REASSURE your friend that this is not their fault.
RESPECT your friendís confidentiality; do not confront the attacker.
EXPECT all sorts of emotions, including lack of emotion and/or shock.
GIVE your friend time. The recovery process is different for each victim and it may take time.