Im Catholic, and I have been going to a Bible study with non-Catholics. At opening prayer, nobody does the sign of the cross. As a Catholic, should I always make the sight of the cross before praying?
As a Catholic Christian you should make the sign of the cross before praying.
“The Christian begins his day, his prayers, and his activities with the Sign of the Cross: "in the name of the Father and of the Son and of the Holy Spirit. Amen”…The sign of the cross… marks with the imprint of Christ the one who is going to belong to him and signifies the grace of the redemption Christ won for us by his cross.
(Catechism of the Catholic Church nos. 2157, 1235).
Cyril of Jerusalem in the fourth century said: “Let us not be ashamed to confess the Crucified. Let the cross, as our seal, be boldly made with our fingers upon our brow and on all occasions over the bread we eat, over the cups we drink, in our comings and in our goings, before sleep, on lying down and rising up, when we are on the way and when we are still.”