The first time i tried quilting by machine, it would all pucker and gather a bit. So what i did was i switched from a regular stitch length to a basting stitch length, and it makes the stitches look a bit more like hand sewing too, and that seemed to work better. The other thing i do now is this. When im quilting i put both hands down on the quilt, with my figers spread eagle lol, and my hands on either side of the pressure foot. I let the quilt move at it's own pace, but i put pressure on the fabric, like how an embroidery hoop will help stretch and hold the fabric taught, and this works really good for me.