1. Whenever you start thinking about your crush's really cute body part (e.g eyes, hair, smile...) imagine that it turns ugly.
2. Whenever you start remembering a good time you had with him/her, force yourself to think about some good time you had with someone else, or think about a fight you two had.
3. Cross out or erase his/her name anywhere you might have written it then drawn hearts around it (e.g your notebook, your textbook, your bedroom wall...)
4. The more you come in contact with him/her, the harder it is to stop your feelings. So at least in the short term, avoid seeing the person often.
5. If you were once dating, or you know that he/she also had a crush on you, you should write the person a letter to get your feelings out and to (softly) explain why you think you should avoid each other and need space.
6. If your crush is really an obsession but he/she doesn't know that you exist, so much the better. You can just avoid him/her without any formality.
7. Focus on your other interests. The more you're thinking about something (or someone) else, the less you'll think about your crush.
8. If you want to develop a crush on another guy/girl as a coping strategy, just do the opposite of the first seven steps.
9. Stop looking at his myspace page every five minutes. If it's a done deal and you're never getting back together with them again, consider deleting his/her off your friends list. You might need to explain to him/her why you are doing this.
10. Another thing that is helpful is just think of all the flaws of your crush

Of the 10 steps, there's only one that might help, step #7 "Focus on your other interests".  Nothing relating to the heart (or hormones) disappears overnight. In time my friend's crush will slowly grow sullen and stale and she'll look back and think herself a silly girl for how she felt. For now, I'll keep the news that I met Ciaran Hinds to myself and not tell her until she's doing a lot better.