I always press to the side now. I turned in 2 blocks for charity quilts and was told that pressing open is incorrect, apparently it can pull open over time or something...supposedly it makes it stronger to press to the side. I grew up with a garment sewer and have seen lots of strong open seams. I gues it is personal preference. I did look it up if you're interested http://www.scrapquilts.com/pressing.html