For normal piecing, I always starch lightly. If I'm doing anything tricky or with bias, I'll starch more heavily. I find it helps me a lot with my accuracy. I did a project several years ago that was all 1/2 square triangles. I starched the heck out of them and had no problems at all. I find that some fabrics don't need much starch, but it's helpful with some. It can make soft fabrics very easy to work with. If I'm doing EPP, I don't starch because it makes it hard to fasten the fabric around the papers and is not needed because the papers stabilize the pieces.