Part III-2. Place for Eucharistic Reservation
52. Where the eucharist is allowed to be reserved in keeping with the provisions of law, only one altar or location in the same church may be the permanent, that is, regular place of reservation.  As a general rule, therefore, there is to be but one tabernacle in each church and it is to be solid and absolutely secure. 
Chapel of Reservation
53. The place in a church or oratory where the eucharist is reserved in a tabernacle should be truly a place of honor. It should also be suited to private prayer so that the faithful may readily and to their advantage continue to honor the Lord in this sacrament by private worship.  Therefore, it is recommended that as far as possible the tabernacle be placed in a chapel set apart from the main body of the church, especially in churches where there frequently are marriages and funerals and in places that, because of their artistic or historical treasures, are visited by many people.
Tabernacle in the Middle of Altar or in Another Part of the Church
54. "The eucharist is to be reserved in a solid and secure tabernacle, placed in the middle of the main altar or on a minor, but truly worthy altar, or else, depending on lawful custom and in particular cases approved by the local Ordinary, in another, special, and properly adorned part of the church.
"It is also lawful to celebrate Mass facing the people even on an altar where there is a small but becoming tabernacle." 
Tabernacle on an Altar Where Mass is Celebrated With a Congregation
55. In the celebration of Mass the principal modes of Christ's presence to his Church  emerge clearly one after the other: first he is seen to be present in the assembly of the faithful gathered in his name; then in his word, with the reading and explanation of Scripture; also in the person of the minister; finally, in a singular way under the eucharistic elements. Consequently, on the grounds of the sign value, it is more in keeping with the nature of the celebration that, through reservation of the sacrament in the tabernacle, Christ not be present eucharistically from the beginning on the altar where Mass is celebrated. That presence is the effect of the consecration and should appear as such.
The Tabernacle in the Construction of New Churches and in the Remodeling of Existing Churches and Altars
56. It is fitting that the principles stated in nos. 52 and 54 be taken into account in the building of new churches.
Remodeling of already existing churches and altars must be carried out in exact compliance with no. 24 of this Instruction.
Means of Indicating the Presence of Blessed Sacrament in the Tabernacle
57. Care should be taken that the faithful be made aware of the presence of the blessed sacrament in the tabernacle by the use of a veil or some other effective means prescribed by the competent authority.
According to the traditional practice, a lamp should burn continuosly near the tabernacle as a sign of the honor shown to the Lord.