It’s the little things in life that matter and it’s the little things in sewing that make a difference.
When I wasn’t sewing lingerie, which has consumed my life as of late, this tip would have been handy. Scratch that. Even when sewing lingerie, this tip is handy. After sewing a seam and pressing it open, I used to arbitrarily trim (or grade) one seam allowance (to reduce bulk). There was no rhyme or reason to which one I cut – I chose based on easiness, which usually depended on what side of the ironing board (and sometimes floor) I was on. But trimming shouldn’t be done mindlessly – there should be reason to it – and the reasoning goes… the stitched edge will fall toward the seam allowance that has been trimmed closest to the stitching. So, if you want the collar to roll slightly to the inside (in other words – you want the top collar to roll to the under collar), trim the under collar seam allowance.