Joseph Fielding Smith Jr. (10th prophet):

The detail in anointing and blessing the sick is as follows: Two or more elders should be called for the purpose. One elder should pour the oil from the bottle containing pure olive oil, which has been consecrated, upon the crown of the head of the sick person. (One drop taken from a medicine dropper is improper, nor should the oil be poured from a spoon.) The brother anointing should not seal the anointing but leave that to the second elder who offers the prayer of administration. The sick person should be called by name in the anointing, and it should be done in the name of Jesus Christ and by authority of the Melchizedek Priesthood according to the revelation, and to the end that the sick person may be healed. After the ordinance of anointing is finished, the elders present, two or more including the one who anointed, will lay their hands upon the head of the sick and offer a prayer in faith in the name of Jesus Christ, and by virtue of the priesthood which they hold seal the anointing. If moved upon by the Spirit of the Lord, the brother who is voice may rebuke the illness and bless with life and health. Prayers and blessings for the sick need not be of great length, that which is essential should be uttered and then the prayer closed in the name of Jesus Christ. After the administration is finished, it is wisdom for the elders who officiate not to prolong their visit but cheerfully withdraw.

Source: Smith, Joseph Fielding. Answers to Gospel Questions. Vol. 1. 147. Salt Lake City: Deseret Book, 1959-1961.