I always pin toward where I want to sew; mainly because when I lie it down and go back later I remember which part I want to sew, very important in piecing. The other thing that I was taught was to put you pins in at an angle; then if you do run over a pin it won't break your needle. I try not to go over pins (especially in piecing) because it can throw the seam off but if I go over putting them in at an angle limits the problems of breaking needles.