The popular Facebook group “Aikido” shares well-written content about the traditional martial art, and the technical notebook.
At the wrist twist of nikyo, you should have uke’s hand firmly pressed on the soft area right below your collar bone, so that there is an angle between uke’s hand and lower arm.
This angle exposes and weakens the wrist. Uke’s arm should be bent. If it is straight, you need to do hijikime osae (sometimes called rokkyo) instead.
When you apply pressure to uke’s wrist, this should be done in the direction of uke’s center. The more you pay attention to this, the more effective the nikyo will be. Apply the pressure in the exact direction of uke’s center. Otherwise, the twisting of uke’s wrist is much less distinct, and the control of uke much less certain.
Apply the pressure until uke has at least one knee on the floor, and is bending the body significantly. This is to avoid uke bouncing right up again, when you release the pressure and spin around to get to the pinning at the end.