Here is the link to the subject how to perform the sign of the cross.
Apparently, there is some debate on whether it is the right shoulder to left shoulder or left shoulder to right shoulder. Either way is correct. Good. I have been feeling out of step on this issue for quite a while. Because I was raised 'high church' Episcopalian, the doctrine teaches the sign to be done right shoulder to left shoulder. It feels right to me since my hand ends up over my heart which has a special meaning for me. The article goes on to say that modern Christians cross themselves left to right. And those who are old church cross themselves right to left. It is a good article and a good resource.