The easiest thing for a father to do is to give advice and directions, for not only has he been there and done that, but he's done so in drifts of snow, flash floods and in increments of 15 miles, all uphill except for the parts that were drops down sheer cliffs. But to raise successful children, fathers must learn to sometimes keep their mouths shut and let them learn their own way. So the mark of a good dad is a callused tongue.