From NewAdvent, Sign of the Cross: "The cross was originally traced by Christians with the thumb or finger on their own foreheads. This practice is attested by numberless allusions in Patristic literature, and it was clearly associated in idea with certain references in Scripture, notably Ezech., ix, 4 (of the mark of the letter Tau); Ex., xvii, 9-14; and especially Apoc., vii 3; ix, 4; xiv, 1. Hardly less early in date is the custom of marking a cross on objects -- already Tertullian speaks of the Christian woman "signing" her bed (cum lectulum tuum signas, "Ad uxor.", ii, 5) before retiring to rest-and we soon hear also of the sign of the cross being traced on the lips (Jerome, "Epitaph. Paulæ") and on the heart (Prudentius, "Cathem.", vi, 129)
Unfortunately, no pictures. Sorry. http://www.newadvent.org/cathen/13785a.htm
What I remember hearing from a friend of mine, a Greek orthodox priest, actually, was that the larger cross, traced from the brow to the chest and then the shoulders, likely arose from the Nestorian heresy, if I remeber him correctly. Two fingers were used when signing the Cross, to indicate the dual natures of Jesus Christ, and a larger motion was adopted to accomodate. The practice moved to three fingers being pressed together, these symbolizing the Holy Trinity, while the other two turned in towards one's palm denote the dual nature of Jesus Christ. The Greeks, however move from right to left, whereas in the Western Churches we move from left to right.
Beyond that, however, I'm not sure of precisely the proper practice. Hope that was some help, though.