I usually press to the dark side. If a lot of seams come together, I will press open. I find that the intersections nest better if they are pressed to one side. I always felt that it made the seam stronger, and the batting wouldn't migrate through. I also used to back stitch at the beginning and end of a piece--I don't do that anymore, but it was hard to break the habit left over from years of garment sewing.
Sue