Years ago, I learned a way to knit a cable that looks even and consistent throughout the piece of knitting. I can’t remember if I figured it out myself, or if I read it somewhere, but it works.
All cables are formed by exchanging the positions of two or more stitches, by crossing a stitch or group of stitches over another stitch or group of stitches. Usually, half of the total number of stitches are held on the cable needle in the front or back; the other half of the stitches are knitted off the left needle, followed by knitting the held stitches. Most books will tell you to knit the held stitches off the cable needle. I do not knit off the cable needle. I find the finished cable looks better, by placing the stitches held on the cable needle back onto the left needle prior to knitting them, rather than knitting them off the cable needle. Also, pull the yarn tighter when knitting the first held stitch, to prevent a hole. The following images show this procedure for a 6-stitch cable held in the back.
Give this technique a try, and your cables will look amazing.