One thing the pattern doesn't mention is how to match the points. Here's what I'm doing:
You can also pin perpendicular on either side of the straight up and down pin. That is probably the better way to go so you can sew with either piece on top. If I see that there is more fabric between the pins on one side than the other, I sew with that piece on the bottom so that the feed dogs help gather up the excess fabric without creating a pleat in my seam.