Excerpted from http://qa.sunnipath.com/issue_view.asp?HD=3&ID=2934&CATE=415

Q. What is the ruling of the sacrifice?

A. The slaughter of  Eid al-Adha (in Arabic: udhiya; in Urdu: qurbani) is a confirmed sunna (sunna mu akkada) and only becomes obligatory if one vows to perform it by saying, for example,  I hereby owe Allah to perform a sacrifice,  or  I hereby owe Allah to sacrifice this animal,  or if one says something like,  This animal is my sacrifice.  Not performing the sacrifice is disliked (makruh), because some scholars (such as the Hanafis) say that it is obligatory. (al-Yaqut al-Nafis fi Madhhab Ibn Idris, 204; Tuhfat al-Muhtaj, 9.346)

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Q. Do I have to slaughter myself?

A. It is sunna for males to slaughter themselves if they can slaughter well, although it is valid to commission (tawkeel) someone else to do it on their behalf. If one cannot slaughter well, or if one is a female, it is sunna to commission someone else to perform it on one s behalf. If one commissions someone else to do it, it is sunna (but not necessary) to be present and witness the actual slaughter.

The Prophet (Allah bless him and give him peace) said to the Lady Fatima (Allah be pleased with her),

Stand up to your sacrificial animal (udhiya) and witness it, for at the first drop of its blood, all your previous sins will be forgiven.  (Hakim)

It is best to commission a Muslim who knows the fiqh of the sacrifice.

If one slaughters oneself, one must intend at the time of slaughtering that this is the sunna sacrifice of  Eid al-Adha. If one commissions someone else to slaughter, one can intend when one authorizes them to slaughter on one s behalf.

(Mughni l-Muhtaj, 4.378; Reliance, j14.3-j14.4; I anatu l-Talibin, 2.335)