Hammer-Ons

I'm wanting to improve my hammer-ons. Any tips or exercises anyone can recommend? Mine are not consistent, plus I'm playing with finger picks on the other hand, so the hammer-on weakness is really apparent. I have one practice song dedicated to left hand only, meaning almost all hammer-ons, and a few pull-offs. Like everything, it's probably just a matter of practice, but any tips or drills would be appreciated.