How do I know what direction to press my seams?
Usually, the seams can be treated in several ways and sometimes it's hard to know which to use though often can be corrected later, but seams are pressed in one direction or the other for several main reasons: 1...so they'll easily fit with other seams when joining two areas where the seams will join or overlap (for example, a row of blocks sewed to a row of blocks will have two seams meeting at the corners of all the blocks...generally then all the seams will have been pressed to one side for one row, but pressed in the opposition direction for the other row so that when joined, the seams from each row will nestle nicely into the other row 2...so a darker colored fabric won't show up around the edges of a lighter one if the seams are pressed toward the dark fabric 3...sometimes also to leave more hand-quilting room since seams are usually too thick to quilt through by hand Some people these days tend to just press all seams open to avoid having to decide, and assume there'll be enough quilting on their quilt to prevent too much stress on any individual seam. And if piecing by hand, which some people still do, the seams aren't actually sewed over so that all options will still be open by the time that seam needs to be sewed to another seam area.
There are two reasons: construction and color show-through. Construction -- When you sew opposing seams it's best for them to be facing in opposite directions, That way they kind of snug up against one another and make a nice tight join. Show through -- The rule of thumb is to press to the dark so you don't have a dark seam allowance possibly showing through a lighter quilt square. Some quilt directions will tell you how to press, but basically you have to think ahead to the construction phase to determine which way is best. Good luck with your quilt project.
When piecing, the first rule is to press toward the darkest block/strip so the seams do not show through on the lightest block/strip. You can also alternate the directions by row so the seams nest, or you can press the seams open, which gives the flattest finish and is the easiest to quilt through.
