Cable panels are typically done with a border of 3 garter stitches on each edge and three reverse stockinette stitches on each side of the twisted stitches. IOW, if you were knitting a piece with three cables it would look something like this:
(RS)K3, P3, work cable, P3, work cable, P3, work cable, P3, K3
(WS)K all the way across
That would give you a nice garter stitch edge and the reverse stockinette stitch background for your cables. You can also use two rev st st on either side of your cables as well. It's personal preference. I'm knitting a pair of gloves for my dad right now that has a cable motif up the front center and I'm only working 2 purl stitches on either side of the braid.