I also have 8 years of union experience. Most of it at winger, inside, and scrumhalf. I think of 2 things when I am sidestepping/deeking someone out on the pitch. First I try to picture a line right down the center of the perspective tackler. Once I am within a step and a half of said tackler I load all of my momentum to one side of that line. This makes the tackler commit to a tackle on one side of their body or to tackling someone in a specific vector if you will. Now once you have sprung your weight onto that one side you want to watch the tacklers hips and or shoulders, as they get set to make a hit where they think you will be you will see the hips and or shoulders square in that direction. As soon as you see that shift you want to explode off the outside of the foot in the other direction. If you have good ball security you can employ a swim move here to break any weak arm tackle being attempted in desperation.