Ditto what everyone said about checking the batting, and another thing to consider is the intended use of the quilt. If it's going to be a wall hanging you can get away with a lot less quilting because it won't be laundered as much. If it is going to be used and washed a lot though I would tend to quilt heavier than the minimum requirement of the batting (for example if the batting indicates minimum of 6" - I would quilt 4").
I personally see no problem with quilting some area's heavier than others. Some area's just dictate more or less quilting because of the design. If for example you are quilting a landscape quilt, it's quite probably that your quilting with be heavier in the trees, bushes, grass etc than it will be in the sky. If it's a traditional block quilt and has a large center block - you may want to quilt the center more or less than the outer blocks, or the borders.
Last edited by DogHouseMom; 05-19-2012 at 12:34 PM.