1. Make sure it is a guy, and not a bear. Bears tend to eye-flirt with their prey, it's a sort of pre-tenderizing process. If it is a guy, proceed to step 3. If it is a bear, proceed to step 2.
2. As savage creatures of death, bears hate music. Especially pop-y "High School Musical"-esque stuff, but no matter what, chances are your friend is going to die. However, all is not lost; depending on the size of your friend, you may have a chance to escape with your life in the 10-15 seconds it takes a bear to eat friends.
3. Assuming this eye-flirter is a guy, access his attractiveness. If he is reasonably attractive, gently elbow your friend and wink at her and proceed to step 5. If he is unattractive, or otherwise offensive to the eyes, proceed to step four.
4. It seems you have encountered what modern teens refer to as a "fugly". The best way to rid your friend of this "fugly" is to refer to her in a loud whisper as "babe" and put your arm around her. If he is not detered by this, a direct approach becomes necessary; look very concerned and loudly whisper, "There is a fugly staring at you". He'll get the point.
5. Huzzah, your friend seems to have attracted the attention of a worthy suitor! After the winking and nudging, alert all of your other friends in the vicinity. Giggle loudly. Make this boy feel uncomfortable, to ensure he can stand the societal pressures that come with being with your friend.
6. If he hasn't run away yet, get his contact information and stalk him for several days, preferably via the internet. Demand your friend to tell you EVERYTHING he's said.
7. Begin to doubt his manliness, I mean, you DID meet him at a musical....
8. Demand your friend to interrogate him about this. Although she may have lost a romantic prospect, you guys may have a new GBF!
9. If he hasn't been scared away yet, he's probably the one. Begin wedding planning immediately, avoid coral on the bridesmaids, and don't invite any bears.