Below is a short clip showing a Ki exercise that helps the student learn to move with a unified mind and body (correct feeling, Ki). Beginners practice this with very little resistance from uke until they can feel the difference between disjointed and unified movement. Over time resistance is increased in order to strengthen the student's center.
The clip below shows how the idea underlying the Ki exercise can be applied to technique; in this case against katate tori.
(Original blog post may be found here