When coming to venerate (kiss) the Holy Gospels, the Cross, honourable Relics and Icons, approach in proper order, without hurrying or crowding one another. Make two prostrations before, and one prostration after, kissing the holy items. The type of prostration, i.e. full prostration (kneeling and touching one’s forehead to the ground) versus a small prostration (a deep bow, touching your hand to the ground), depends upon the day of the week. When venerating icons of the Savior, one should kiss His feet; or, if He is depicted to the waist, His hand. When venerating Icons of the Mother of God and of the Saints, kiss the hand. On Icons of the Savior Not-Made-by-Hands or of the Beheading of St. John the Baptist, kiss the hair.
Although an Icon may bear the images of several Saints, when a number of the faithful are approaching to venerate the Icon, one should kiss the Icon only once, so as not to delay the others, and to maintain proper order in the church.
Before the Icon of the Savior, one may say the Jesus Prayer: "Lord Jesus Christ, Son of God, have mercy upon me a sinner," or the prayer "I have sinned immeasurably, O Savior, have mercy upon me."
Before an Icon of the Most-holy Theotokos, one may say the prayer, "O Most-holy Theotokos, save us."
Before the Honorable and Life-giving Cross of Christ, we say the prayer "Before Thy Cross, we bow down, O Master, and Thy Holy Resurrection we glorify." We follow the prayer with a prostration.
(From the book First Steps Within the Church)