I think it's important to post again about when one should bow or genuflect. I know that some people at my parish didn't think we should genuflect to the Crucifix on Good Friday, but you actually do according to the Church. Here are some facts on genuflecting and bowing.
Disclaimer: This post does not express my endorsement of the entirety of the GIRM. I do not necessarily support everything in the GIRM or any post-Vatican II document in its entirety or any of its parts.
General Instruction of the Roman Missal (GIRM 2003):
274. A genuflection, made by bending the right knee to the ground, signifies adoration, and therefore it is reserved for the Most Blessed Sacrament, as well as for the Holy Cross from the solemn adoration during the liturgical celebration on Good Friday until the beginning of the Easter Vigil.
275. A bow signifies reverence and honor shown to the persons themselves or to the signs that represent them. There are two kinds of bows: a bow of the head and a bow of the body.
A) A bow of the head is made when the three Divine Persons are named together and at the names of Jesus, of the Blessed Virgin Mary, and of the Saint in whose honor Mass is being celebrated.
B) A bow of the body, that is to say a profound bow, is made to the altar; during the prayers Munda cor meum (Almighty God, cleanse my heart) and In spiritu humilitatis (Lord God, we ask you to receive); in the Creed at the words Et incarnatus est (by the power of the Holy Spirit . . . made man); in the Roman Canon at the words Supplices te rogamus (Almighty God, we pray that your angel). The same kind of bow is made by the deacon when he asks for a blessing before the proclamation of the Gospel. In addition, the priest bows slightly as he speaks the words of the Lord at the consecration.
Also, please remember to genuflect by touching both knees to the ground before entering the pew when the Holy Eucharistic is visible on the altar in Adoration. This will also occur if you arrive at Mass after the Consecration. In these two cases touch both knees to the ground, make the sign of the Cross, and bow.
Source: 2003 GIRM