I'm not an addict but have lots of experience with them.
As a loved one of an addict, one of the most helpful things I learned were the "three Cs":
You didn't CAUSE their problem;
You can't CONTROL them; and
You can't CURE them.
I think "tough love" is generally effective, if you are referring to setting and sticking to boundaries of acceptable behavior from an addict. It doesn't mean that you have to hate them, it means that you will always support them as they seek recovery, but not if they remain in active addiction.
One book that is cited again and again by loved ones of addicts is "Codependent No More" by Melanie Beattie. Excellent reading.
Also, you might Google and do some reading on the term "loving detachment."
Finally, you might want to check out the Loved Ones forums on this site, too...lots of wisdom there.
Good luck, and please protect your own sobriety first!
That is the most important thing...everything else is secondary.