I usually press to the dark side but I also take into consideration if there are lots of seams and then I take a look at which piece has the most seams in it already and then press the other way. Sometimes is is a free for all and the seams whisper to me they want to go left or right. I let them go the way they want. The leader of my quilt has been converted to open seams and it works most of the time....for her. Do what seems to be best for that quilt!