Prayer is conversation or speaking with God. Prayer is an integral part of an Orthodox Christian's daily life. Prayer is necessary. It is as necessary as eating, sleeping and breathing. Everything we have comes from God. Therefore, we must pray to God at all times - in times of joy and in times of despair. And we must of course, rely on His holy will - for only God knows best.
Orthodox Christians use the sign of the Cross whenever we pray as a visible sign of our faith. The first mention found in history of Christians making the sign of the Cross is from the 2nd Century. Writings indicate that Tertullian of Carthage, an early Church Father, said: "In all our travels and movements, in all our coming in and going out, in putting of our shoes, at the bath, at the table, in lighting our candles, in lying down, in sitting down, whatever employment occupieth us, we mark our foreheads with the sign of the cross".
Jesus Christ saved us from the power of sin and eternal death through his death and resurrection. He conquered not only sin, but death itself! He arose from the dead making the Cross His victory over sin and death. Therefore, the Cross is a sign of this great victory!
The rest is up to us. If we truly wish to be delivered from the power of sin - we must follow Christ! We must believe in Christ. We must fulfill His holy will and be obedient unto Him. And, in order to express our faith in Jesus, we wear a cross on our bodies and during our prayer time that is so essential, we form the sign of the Cross over ourselves.
In order to make the sign of the cross, we use our right hand and bring the tips of the first three fingers together (thumb, index finger and middle) representing our faith in the Trinity - God the Father, God the Son, and God the Holy Spirit who are of one essence and indivisible. The last two fingers are bent down to show that the Son of God came down to Earth from Heaven and had two natures - always being God and also becoming human.
We take our fingers, in this position, and touch our forehead for the blessing of our mind. We then touch our stomachs for the blessing of our internal feelings. We then touch our right and then left shoulders for the blessing of our bodily strength. These four points also refer to the four points on the Cross at Calvary.
The sign of the Cross gives us great strength and should never be used absent-mindedly as that would be sacrilege. We make the sign of the Cross always keeping in mind what it is symbolizing at the beginning of prayers, during prayer and at the end of prayer. We may also use the sign of the Cross when we enter the church and when we draw near to anything we consider holy such as the Cross or an icon. We can also use the sign of the Cross at important moments to indicate our prayer of praise or for mercy at times of joy, danger or sorrow.
When making the sign of the Cross we say aloud or mentally, "In the name of the Father, and of the Son, and of the Holy Spirit. Amen. " This expresses our faith in the Holy Trinity. "Amen" means 'so be it' or 'in truth'.