cant believe this hasent been said before. To make great score lines, use a metal tip mechanical pencil without the lead, personally i use the non-cutting side of my exacto, you will still be able to see your dash/dot lines to make your folds. this is the best way, used by most papercrafters, mainly because most papercrafts have textures printed out, and this method will not ruin the printed texture. it easier to use than a butterknife, and more accurate than a ball point pen.