|Getting a peter pan collar matched up perfectly on center can sometimes be tricky. But I figured out a trick that makes the collar meet perfectly every time.
First of all, after you've turned and ironed the collar, bar tack it together right where you want it to meet. The next step requires you to not iron the front of the dress/blouse after you've cut it out. After all, they're cut on the fold, so you have a center line to match the collar center to. Pin the center first, and then the rest and sew it in one piece.