I start at the middle and work my way outward changing direction with each line. I also use chalk or the new heat pens to draw where I need to be quilting. I also have my walking foot on the machine and go slowly across. All of this together will give me what I want. I found out the hard way if I leave one step out I will end up with curves and puckers.
Using a low tufted batting or all cotton batting ( W&N) works the best.