I would advise against stitch-in-the-ditch. Very nerve-wracking and slow to do. Straight or wavy lines are fast and easy to do with a walking foot. The nice thing about wavy lines is that they do not need to be evenly spaced apart, making them faster and easier than even just straight lines that are not in the ditch. I will try to attach a couple of examples:
http://www.bijoulovelydesigns.com/20...-tutorial.html
https://www.youtube.com/watch?v=CvBjmFimpgA
Also, I highly recommend heavily starching the backing fabric and the top before you sandwich. This stabilizes the fabrics so they are much less likely to shift or stretch while you are working, minimizing the possibility of tucks or puckers.
Edit: I agree with accordion-pleating the quilt that is under the arm of the machine. This worked much better for me than rolling. A roll can get somewhat stiff and unwieldy; the loose accordion pleats are easier to adjust as you work.