I found half stitch really difficult when I started, and this is how I made sense of it. There are many ways to make half stitch for different effects but for the beginner ribbon, this helped me.
Half stitch has a different rhythm to cloth stitch.
One of the worker pair (Fred) makes a new 'friend' at each half stitch. You can see Fred weaving across through the passives as you work, leaving behind his new 'friend' at each stitch, going off with a new 'friend' and leaving a horizontal, single thread weaving from side to side.
If you lose track, find the horizontal thread coming from the pin, that is Fred.
If you use two twists around the pin, Fred will stay as your main worker. This means you can keep control of the tension on the last row or two.
If you have passives to work in cloth stitch at the edge of a piece, use Fred and the friend he is with. When you reach the passives work through with cloth stitch. on returning to the half stitch ground, put extra twist on Fred and friend so Fred is always leading.
