From the Revised General Instruction of the Roman Missal

The following is the means by which the Precious Blood may be administered to the faithful. It is from the revised General Instruction of the Roman Missal also knowns as the GIRM:
Communion under Both Kinds

281. Holy Communion has a fuller form as a sign when it is distributed under both kinds. For in this form the sign of the eucharistic banquet is more clearly evident and clear expression is given to the divine will by which the new and eternal Covenant is ratified in the Blood of the Lord, as also the relationship between the Eucharistic banquet and the eschatological banquet in the Father's Kingdom.105

282. Sacred pastors should take care to ensure that the faithful who participate in the rite or are present at it are as fully aware as possible of the Catholic teaching on the form of Holy Communion as set forth by the Ecumenical Council of Trent. Above all, they should instruct the Christian faithful that the Catholic faith teaches that Christ, whole and entire, and the true Sacrament, is received even under only one species, and consequently that as far as the effects are concerned, those who receive under only one species are not deprived of any of the grace that is necessary for salvation.106

They are to teach, furthermore, that the Church, in her stewardship of the Sacraments, has the power to set forth or alter whatever provisions, apart from the substance of the Sacraments, that she judges to be most conducive to the veneration of the Sacraments and the well-being of the recipients, in view of changing conditions, times, and places.107 At the same time, the faithful should be encouraged to seek to participate more eagerly in this sacred rite, by which the sign of the Eucharistic banquet is made more fully evident.

283. In addition to those cases given in the ritual books, Communion under both kinds is permitted for

1. Priests who are not able to celebrate or concelebrate Mass;
2. The deacon and others who perform some duty at the Mass;
3. Members of communities at the conventual Mass or "community" Mass, along with seminarians, and all who are engaged in a retreat or are taking part in a spiritual or pastoral gathering.

The Diocesan Bishop may establish norms for Communion under both kinds for his own diocese, which are also to be observed in churches of religious and at celebrations with small groups. The Diocesan Bishop is also given the faculty to permit Communion under both kinds whenever it may seem appropriate to the priest to whom, as its own shepherd, a community has been entrusted, provided that the faithful have been well instructed and there is no danger of profanation of the Sacrament or of the rite's becoming difficult because of the large number of participants or some other reason.

In all that pertains to Communion under both kinds, the Norms for the Distribution and Reception of Holy Communion under Both Kinds in the Dioceses of the United States of America are to be followed (see nos. 27-54).

284. When Communion is distributed under both kinds,

1. The chalice is usually administered by a deacon or, when no deacon is present, by a priest, or even by a duly instituted acolyte or another extraordinary minister of Holy Communion, or by a member of the faithful who in case of necessity has been entrusted with this duty for a single occasion;
2. Whatever may remain of the Blood of Christ is consumed at the altar by the priest or the deacon or the duly instituted acolyte who ministered the chalice. The same then purifies, wipes, and arranges the sacred vessels in the usual way.

Any of the faithful who wish to receive Holy Communion under the species of bread alone should be granted their wish.

285. For Communion under both kinds the following should be prepared:

1. If Communion from the chalice is carried out by communicants' drinking directly from the chalice, a chalice of a sufficiently large size or several chalices are prepared. Care should, however, be taken in planning lest beyond what is needed of the Blood of Christ remains to be consumed at the end of the celebration.
2. If Communion is carried out by intinction, the hosts should be neither too thin nor too small, but rather a little thicker than usual, so that after being dipped partly into the Blood of Christ they can still easily be distributed to each communicant.

286. If Communion of the Blood of Christ is carried out by communicants' drinking from the chalice, each communicant, after receiving the Body of Christ, moves and stands facing the minister of the chalice. The minister says, Sanguis Christi (The Blood of Christ), the communicant responds, Amen, and the minister hands over the chalice, which the communicant raises to his or her mouth. Each communicant drinks a little from the chalice, hands it back to the minister, and then withdraws; the minister wipes the rim of the chalice with the purificator.

287. If Communion from the chalice is carried out by intinction, each communicant, holding a communion-plate under the chin, approaches the priest, who holds a vessel with the sacred particles, a minister standing at his side and holding the chalice. The priest takes a host, dips it partly into the chalice and, showing it, says, Corpus et Sanguis Christi (The Body and Blood of Christ). The communicant responds, Amen, receives the Sacrament in the mouth from the priest, and then withdraws.