I have learned
I no longer buy as many "precuts", I buy yardage and fatquarters.
I wash all my fabric.
I starch all my fabric (I spray it and let its soak in)
I then press all my starched fabric.
I prefer a heavy starch, it makes cutting and piecing much easier.
It is more work yes, but for me it's worth it and I have much better results.
I also take my time when sewing and I am happier with my results.
YMMV