"In the name of the Father, and of the Son, and of the Holy Spirit. Amen."
This is the traditional formula used in many Christian denominations.
Here's how to say it while making the sign of the cross:
1. Start with your right hand. Touch your forehead and say, "In the name of the Father."
2. Move your hand down to your chest and say, "and of the Son."
3. Move your hand to your left shoulder and say, "and of the Holy Spirit."
4. Finally, move your hand to your right shoulder and say, "Amen."
This is the most common way to say the Sign of the Cross, but there may be slight variations in phrasing depending on your denomination or tradition.