I pin perpendicular to the edge of the fabric, but only when needed to match a seam or points. I'm trying to change old bad habits by removing them before sewing over them!

I sometimes do both in one seam. Pinning parallel to the cut edge at 1/4 inch lets me see that previous seams will match up; it's especially helpful when a diagonal seam meets a right-angle seam and I'm sewing the patches together. (is this making sense?) I always have the head of the pin toward me, and pull out slowly as I stitch toward it. But in general, pinning perpendicular to the cut edge is recommended because the wiggle of fabric along the seam line is less.

I put pins in at an angle. I can sew over the matching seam and not hit the pin. I can then take the pin out without the matching points being moved at all.

I rarely pin but when I do I pin so they are easy to remove as I'm stitching. When piecing for a double wedding ring I use 3 pins - one at each end and one in the middle.

Jan, Are you left handed? If not, why is this a better way than with the head to the right for easy removal? Just interested in your thoughts. Not being critical. Yolanda Wood River

I have always pinned perpendicular with the heads to the right, then I got a fancy guide with my machine and have to pin with the heads to the left. I also glue intersections as well as pin around them.

I pin across the seam line but I pin very little when I'm piecing. I hate pulling the pins out as I sew and I find that the pins tend to distort if I'm not careful. Generally, I'll use a pin to "match" points. Pinning is very much a matter of personal preference though. I've watched members of my quilt group work at the machine when we're doing quilts for donation and the pinning is all over the map. Whatever works for you is probably the best approach here.

If I pin (not very often except for matching seams), I pin perpendicular with heads to the left. I'm right-handed so right hand is guiding the fabric, left hand removing any pins after the needle hits them and wakes me up .... LOL

Oh, sometimes for a border or other long piece or for a big applique I do pin parallel, seems to give me more hold per pin. Heads toward me, remove pins as I get to them.

When I first learned to sew, I followed the teacher's directions and pinned perpendicular to the seam line. (And sewed over the pin-I'm still a rebel.)
Then came THE SERGER! Yep! Ran right into the sucker! The pin flew in bits all over the place, really scared me. Put a damper on my using the serger until I had it cleaned, retimed and the cutter replaced.
Not wanting to repeat the error. I started putting pins parrallel to the seam, to the left, so they didn't need to be removed.
Eventually I realized it's the seam that needs to match, not the edge of the fabric. So now I pin baste the seam line. When the machine gets close to a pin, I hold the head with my finger nail and let the machine pull the fabric off of the pin. This way, I don't have to stop the machine to pull out those perpendicular pins.

So, my vote is parrallel.

I pin both ways, even in one seam. Can't explain why, I just do it unconsciously.