The prayer that was prayed at the beginning of Vatican II:
We are here before You, O Holy Spirit, conscious of our innumerable sins, but united in a special way in Your Holy Name. Come and abide with us. Deign to penetrate our hearts.
Be the guide of our actions, indicate the path we should take, and show us what we must do so that, with Your help, our work may be in all things pleasing to You.
May You be our only inspiration and the overseer of our intentions, for You alone possess a glorious name together with the Father and the Son.
May You, who are infinite justice, never permit that we be disturbers of justice. Let not our ignorance induce us to evil, nor flattery sway us, nor moral and material interest corrupt us. But unite our hearts to You alone, and do it strongly, so that, with the gift of Your grace, we may be one in You and may nothing depart from the truth.
Thus, united in Your name, may we in our every action follow the dictates of Your mercy and justice, so that today and always our judgments may not be alien to You and in eternity we may obtain the unending reward of our actions. Amen.
This prayer was composed by St. Isidore of Seville, to be used during the Second Provincial Council of Seville, Spain, in 619. It was also used during the Fourth Provincial Council of Toledo, Spain, in 633. With this prayer the sessions of the First Vatican Council began in 1869. It was said in Latin before every morning meeting of the preparatory commissions and conciliar commissions of Vatican II.
I cannot think of a better or more beautiful prayer for a beginning.
Found it here.