Marking your quilt top

[juliefugate]

I have a quilt I'll be quilting soon. I have a longarm, but will be doing my first very detailed and extensive quilting wit h lots of ruler work and feathers, etc. (I usually do free motion). This is a very special quilt and it has a white background. What do you use to mark the top for quilting? I'm really afraid of ruining this amazing quilt with marks that don't come out.