I rarely pin, but when I do I use the flat head flower pins. More important than the pins, I think, is how you use them. I do not pin at a 90 degree angle from the edge of the fabric. Instead I pin seams at a 45 degree angle, with the pin going in lower on the edge and angled up to the left. This allows me to sew closer to the seam intersection and actually catch the seam allowances before I slide out the pin, not so much by pulling it,but by holding onto it as the feed dogs pull the fabric away from me. Try it - you'll like it!