It depends on which razor I'm using (smaller razors need a different grip) as well as where I'm shaving. Small razors I have index finger on the spine and my middle finger on the tang; larger blades I use 2 fingers on the spine and ring finger on the tang. If I'm going ATG or on the neck I'll almost always use the '1 on the spine, one on the tang' grip, as it gives me a lighter touch. As long as you have a firm grip on the blade and good control over the blade angle, whatever works well for you is the right way to hold it.