For a low Mass:
The Gloria Patri is either replaced by Requiem AEternam or omitted.
The sign of the cross at the Introit is made over the missal rather than on the celebrant
The Agnus Dei is “Agnus Dei qui tollis peccata mundi, dona eis requiem” and the third time is added “sempiternam” (and so the priest does not strike his breast)
“Requiescant in pace” is said instead of Ite Missa Est
All Collects (and associate Secrets and Postcommunions) not for dead are not said, even if they are commemorations or collects imperata (i.e. a collect commanded to be said at almost all Masses for some important cause) unless this is of the dead.
And all these are omitted:
The Iudica Me
Gloria in excelesis
The blessing before the Gospel is and the kissing of the Gospel at the conclusion.
The Credo
The blessing of water at the Offertory
The prayer for peace “Domine Iesu Christe qui dixisit Apostolis tuis”
The final blessing
If the low Mass is the funeral Mass then the absolution after the Mass is compulsory (and according to the 1962 rubrics the Last Gospel is accordingly omitted)
One peculiarity of the *text *of the Requiem is the Offertory consists of verses and the antiphon instead of just the antiphon. For which reason in the 1962 missal while the other Masses are usually titled “Antiphonam ad Offertorium” the Offertory for the Dead is titled “Responsorium ad Offertorium” Likewise for the Communion.