Boy, you did open a can of worms with this one. My addition is that I pre-wash everything for all of the pre-listed reasons. I do buy yard sale fabrics, so previous storage can be an issue. Also, because while working on a Log Cabin block, using un-prepped fabric, one strip shrunk so bad it pulled from the seam under the iron. So, pre-wash and dry like I intend it to be used for once finished, starch before cutting (keeps it's shape better, especially on the bias), pre-wash and dry the batting, then wash and dry again, once the project is finished. This gets rid of any residue from starch, glue basting and general handling.