i've tried several methods of marking my quilts for handstitching: chalks, pencils, pens. no one method is perfect and i was unhappy with each of these for various reasons. then i read a tip from aneela hoey describing her hera marker. love it!
it's rather like a bone folder used for scoring paper - only it scores your fabric. i just run it down the side of the quilting ruler (below) and it leaves me a nice crease to follow (above). i don't have to worry about it showing up based on the color of my fabric or about it smearing, fading, or not erasing. it stays put until the stitching is done, even if i leave it for several days (weeks). perfect.
other than that, it's my favorite!