How do you bless yourself before the gospel?

Before the Gospel is read or sung at Mass, the priest seeks to worthily proclaim the Gospel and prays to God for the grace to do so. At High Mass, a deacon or priest asks the celebrant (according to the 1962 missal):

Deacon/Priest: "Pray, sir, a blessing"

Celebrant: "The Lord be in thy heart and on thy lips, that worthily and becomingly thou mayest announce His Gospel: In the name of the Father, and of the Son [here priest gives his blessing] and of the Holy Ghost. Amen."

Both the priest and congregation then make a triple sign of the cross with the blade of their thumb on their forehead, lips and breast when the priest/deacon begins, "The following is taken from the Holy Gospel according to..."

This triple reverence is to signify that the faithful wish that the Gospel be on our minds, on our lips and in our hearts. It is to spur us to pay greater attention that the Gospel may not fall on deaf ears and that it will find fertile ground in the listener, much like the parable of the sower (St. Matthew 13:1-23, St. Mark 4:1-20, St. Luke 8:1-15).