From the 1984 Ceremonial of Bishops :
“69 A genuflection, made by bending only the right knee to the ground, signifies adoration, and is therefore reserved for the blessed sacrament, whether exposed or reserved in the tabernacle, and for the holy cross from the time of the solemn adoration in the liturgical celebration of Good Friday until the beginning of the Easter Vigil.
70 Neither a genuflection nor a deep bow is made by those who are carrying articles used in a celebration, for example, the cross, candlesticks, the Book of the Gospels.
Reverence toward the blessed sacrament
71 No one who enters a church should fail to adore the blessed sacrament, either by visiting the blessed sacrament chapel or at least by genuflecting.
Similarly, those who pass before the blessed sacrament genuflect, except when they are walking in procession.
Reverence toward the altar
72 A deep bow is made to the altar by all who enter the sanctuary (chancel), leave it, or pass before the altar.”
From the 2010 English translation of the General Instruction of the Roman Missal, n. 274:
“During Mass, three genuflections are made by the Priest Celebrant: namely, after the elevation of the host, after the elevation of the chalice, and before Communion. Certain specific features to be observed in a concelebrated Mass are noted in their proper place (cf. nos. 210–251).
If, however, the tabernacle with the Most Blessed Sacrament is situated in the sanctuary, the Priest, the Deacon, and the other ministers genuflect when they approach the altar and when they depart from it, but not during the celebration of Mass itself.
Otherwise, all who pass before the Most Blessed Sacrament genuflect, unless they are moving in procession.
Ministers carrying the processional cross or candles bow their head instead of genuflecting.”
The Sign of the Cross is not part of a genuflection.
[Excerpt from the English translation of Ceremonial of Bishops © 1989, International Commission on English in the Liturgy Corporation (ICEL). Excerpt from the English translation of The Roman Missal © 2010, ICEL. All rights reserved.]