I don't find diamonds particularly difficult either. But like mic-pa, I pin ALOT. Maybe it's the visual that's throwing you off because when you put things right sides together the ends hang over? Seams should still nestle but I usually press open (on all my quilting, not just diamonds) so that it's easy to see where the seams meet. Lay your fabs right side together, put a pin straight down into the top seam, go through to the bottom fab and put your pin straight into that seam. Holding the pin straight up/down (perpendicular to your fabric) then put pins parallel to the fabric as close to your up/down pin as possible. Repeat for each seam. The ears on the ends should still hang over 1/4 on each end.