practice, practice, and more practice. It took me 6 weeks to perfect it. You'll find your own way of doing it. I found out really early to that I had to use a circular needle (knitpicks)to do it. Otherwise the straight needles would fall to the floor or in my lap. Then I had to find the right cable needle, for me. Stores don't sell straight cable needles...and i wasn't going to use those other kinds, so I use the thick, blue yarn/tapestry needle. The plastic one. if I used the metal ones the stitches would slip right off. It's just like when I started knitting......I had to find the right way to do it and you will find yours. I knit nothing but cables now.
You will get it, just keep trying