Jeanette, tension adjustment is indeed the key. You will need to make a sample quilt sandwich using the same weight fabric and batting that you will use in your quilt. I would suggest using a light/dark fabric, to contrast whatever thread you are using. That way you will see the results better. If you are doing free motion quilting then test using that method. Continue to change the tension adjustment until you no longer see the bobbin thread. At this point, I turn my sample over to see if all is well on the back. If you move your work too fast for the speed of the machine, you will find that the bobbin thread is too tight as it didn't have time to advance in the shuttle correctly. I make a decent size sample to practice on and get my speed and rythm down. Hope these tips were helpful. :D