Like others
I starch and square up fabric before cutting it.
I square up each block component of a block before making the block and starch
I square up every block and starch
I square up the top prior to putting it on the longarm
I square up the top prior to sewing on the binding
Yes, I use a lot of starch, but I can fold a top and it will remain wrinkle free when unfolded. At the end of the day I have only achieved a perfectly square quilt on a few occasions and I am fine with that. As long as it is not totally off I am happy, but I still search out tutorials and tidbits from others for all things quilty.