Pressing fabric for quilting is almost as important as sewing if you want to get crisp accurate seam lines. After sewing two pieces together I go to the iron and press down on top of this stitching. This will help nestle the threads into the fabric. Sometimes this is referred to as registering the seam. With few exceptions, I usually do not open seams when I press. Instead I press both seams to one side of the fabric. This pressing is based on construction concerns not the old adage ‘always press to the dark’.
Some patterns include directions for pressing fabric for quilting. Look for these patterns as it will make construction of your block easier.