Hi Jean,
I put a knot in my thread, put the needle through the back of the fabric about an inch away from where you will bring your needle up at into the top of the quilt -once you come through the top of the quilt with your needle just tug on your needle so that the knot that is resting on the backing of the quilt will "pop" through just the backing. It nestles itself into the batting. When I finish a length of thread or a row of quilting I finish with the needle to the back of the quilt , I wrap the thread twice around the needle ( Like you are going to make a french knot - if you know embroidery stitches) and I put the needle back through the hole that the thread is coming out of and bring the needle back up about an inch away and again tug that knot through - trim the thread flat with the back of the quilt.
I hope this is making sense . :? . get out something to practice on and just practice starting and stopping and you will get the hang of it.
To mark my quilts I use Dixon Cloth Markers ( they are kind of like waxy chalk) They come in red, green , blue and white ... Blue works on most every color fabric even dark ones. I make lots of scrap quilts and these seem to work best for me.
Deb