The old rule of thumb was to place your hand over an area and if your hand does not touch the quilting, then you should do more. Mainly, this area should be less then 4" square or so. They used to judge quilts in this manner. Now it is a different story. If the quilt is going to be on a bed, then the top of the quilt where the hands use it should be quilted more. I hope this helps you to understand. I am planning to make a duvet cover to match my drapes and I think I will make the sides longer and quilt it every 1" or so in rows to help keep it on the bed. (My husband will appreciate this)