I Iron everything. Prewash, Iron, fold, put away. Get out, cut. sew. iron. Only time I Press is if I finger- press a seam that will be crossed with another seam before I iron it cause I am too lazy to get up and iron it. Or if I am working with 60 degree angles. I usually finger press those. I found it interesting that so many here said what they did but not so much "why". It seems to me that pressing takes longer and can cause tucks along the seam line if you aren't careful. As long as I iron with the grain (the direction the threads run) the pieces don't stretch. And yeah, I stay away from steam while piecing, but after washing that steam sure helps get out the wrinkles. Magic Sizing is better than starch for removing wrinkles. The starch just stiffens the fabric so it doesn't stretch when working with triangles. That is the way I see it anyways.