It depends on the look you wish to achieve at the end. For some I have used satin stitch, but when I do is when I want a drawing look, and I use a dark color thread. I have also used a blanket stitch, either single or double. Single with a thin thread if I don't want it to be very noticeable, double with a 40 wt thread if I want to bring it up. If I want raw edge I make a straight stitch inside the edge and very close to it, but not touching the edge. Just by sewing this line the fraying may begin, but will stop at the line and the frayed border is not too wide. I had to mentally prepare myself for this one because I don't like frayed edges, but some quilts lend themselves to it.