From the Ceremonial of Bishops:
“72. A deep bow is made to the altar by all who enter the sanctuary (chancel), leave it, or pass before the altar.”
“76. The bishop is greeted with a deep bow by the ministers or others when they approach to assist him, when they leave after assisting him, or when they pass in front of him.”
(Ceremonial of Bishops, Liturgical Press, 1989, ISBN 0-8146-1818-9, page 38).
From the 2002 General Instruction of the Roman Missal (GIRM) approved for the USA, which can be accessed from romanrite.com/girm.html :
“277. … Before and after an incensation, a profound bow is made to the person or object that is incensed, except for the incensation of the altar and the offerings for the Sacrifice of the Mass.”
“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); …”
“160. … When receiving Holy Communion, the communicant bows his or her head before the Sacrament as a gesture of reverence and receives the Body of the Lord from the minister. The consecrated host may be received either on the tongue or in the hand, at the discretion of each communicant. When Holy Communion is received under both kinds, the sign of reverence is also made before receiving the Precious Blood.”
“49. When they reach the sanctuary, the priest, the deacon, and the ministers reverence the altar with a profound bow.” (This is for the entrance procession.)
“274. … If, however, the tabernacle with the Most Blessed Sacrament is present 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 heads instead of genuflecting.”
“43. … Those who do not kneel ought to make a profound bow when the priest genuflects after the consecration.”
“185. If a prayer over the people or a solemn formula for the blessing is used, the deacon says, Inclinate vos ad benedictionem (Bow your heads and pray for God’s blessing).”
“90. The concluding rites consist of …
d. The kissing of the altar by the priest and the deacon, followed by a profound bow to
the altar by the priest, the deacon, and the other ministers.”
The GIRM’s index lists the following for the word “bow”:
43, 49, 90, 122, 132, 135, 137, 143, 160, 169, 173, 175, 185, 186, 195, 211, 222, 227, 230, 233, 251, 256, 262, 272, (Heading before) 274, 274, 275, 277, 330
I think I have included everything that would apply to an altar server. There are more instructions on bows for priests, deacons and concelebrants.