Good question… I’ve never had it laid out to me a “proper” way to do this. I live in New Mexico, where most people are Mexican, or Spanish ancestry. I notice most people around here also adding a kiss upon their hand at the end of the maneuver, but I don’t know what that means. I’ve always thought that the form of it is not very important. How you do it, or whether you do it, it is a sacramental that is of value only to the extent that you’re uniting with Jesus in the doing of it. Lately I’ve tried to be more reverential about it, making a more deliberate, slow, full crossing from forehead to navel, shoulder to shoulder. I keep a small container of holy water at my front door and dip my finger in it and cross myself when leaving the house. Helps to remind me to whom I belong as I proceed into public.