Theres really no rules but here is what I do just to prepare myself for mass and to offer God my intentions.
First I will say the Act of Contrition
Then an Our Father, Hail Mary and Glory Be for the intentions of the Pope, and then I say this folowing prayer that is self explainitory:
Eternal Father, I unite myself with the intentions and affections of our Lady of Sorrows on Calvary and I offer Thee the Sacrifice which Thy Beloved Son Jesus made on the Cross, and now renews on this holy altar:
First: To adore Thee and give Thee the honor which is due to Thee, confessing Thy supreme dominion over all things, and the absolute dependence of everything upon Thee, Thou Who art our one and last end.
Second: To thank Thee for countless benefits received.
Third: To appease Thy Justice provoked by so many sins, and to make satifaction for them.
Fourth: To implore grace and mercy for myself, for (name), for all afflicted and sorrowing, for all poor sinners, and for the holy souls in Purgatory.
Hope this helps!