I have used the crayola markers too. I made a heirloom christening gown, and marked the center in yellow. I just know it didn't come out. I must have ironed it. I have used a sharp mechanical pencil too. On light colored fabric it works well. In applique by the time you get the piece appliqued a great deal has already worn off. I got a frixon pen for christmas and am looking forward to using it. I took a Shar Pederson class at quilt festival and it was on navy fabric. She had a white pen that we used--i would have to go and see if I can find it to tell you the name, but when you iron it it comes off. I have used silver water color pencils (and yellow) for marking quilts on black. It works well.

I think it best to experiment and try different methods and see what works best for you. Chalk for me doesn't last very long, so I try and do this right before I quilt.
Oh, and I also got a mechcanical pencil that erases as well as washing out.

try "Multi-Pastel Chalk Pencils" from General Pencil Co in white and light grey
Also the ceramic mechanical pencil (Fons and Porter, Sewline, Collins) in white
A slection of colors from Bohin - but in white

I recommend avoiding colors as some have lots of color pigment in them and difficult to come out.
Everyone has their favorite and I don't believe there is one "best" markeer because often what works for one person doesn't work for another.

"Multi-Pastel Chalk Pencils" from General Pencil Co in white and light grey

I like these the best for this type of products but they are hard to find. Amazon does cary them.

I like regular chalk board chalk. I sharpen the end with a crayon sharpener to get a fine line. Just be careful of the colored chalk because it may not come out, check the color on the same fabric as the quilt each time before using colors.

Thanks everyone for the great ideas. Guess I will have to go shopping for some different kinds of marking tools.

I like the wash out blue pens and the dissapearing ink pens best.
I have the chalk squares but they dont work with stencils. Pounce only works on some fabrics but wont show on others if they are light colors so is a problem on quilts with mixed colors. The blue pounce isnt much better. It does help to lightly wet the fabric with water before you pounce.

I just used a frixion pen to mark my quilt - quilted it...threw it in the machine to wash but all the lines did not come off. Now question? If I dry it in the dryer and then iron, will the lines come off? I don't think I will ever use this pen again. (It would have helped if I'd have know about the ironing before I threw it in the wash.) Any suggestions?