It's mainly a matter of more experience. In the beginning it's natural to try to throw your uke using your own strength. As you gain experience you'll get better with timing and movement so that uke is throwing himself to get out of the pain induced by your technique. Sometimes just an inch more movement in one direction or another is enough to do the trick.
Here's a video I found that you might find helpful:
https://www.youtube.com/watch?v=T9vWR7EdQdM
[Edited to add...] Also, don't forget to REALLY work on basics: move from one point, extend ki, etc.
Yours in Budo,
---Brian---