At the moment, I'm proud to say I have accurate 1/4" seams and all of my 16, 2" squares match up perfectly. I credit this to starch, almost accurate cutting, my sticky note pad which is lined up next to the presser foot to ensure a 1/4" seam, and nesting my seams. It's only taken me a few quilts to reach this point, but I finally made it!
Good luck.