Reading back, no one is a saint. What lessons have they learned from it? We've all done stupid crap.
Frankly, Clinton should have said, "Yeah, I did inhale. I was a college kid who was finding out about the world, and I learned that a) it's not for me and b) it's illegal. Haven't done it since. Learned my lesson." For example (yes, that was an easy example).
Own up to past youthful indiscretions. Heck, RELY on them to show that you have matured and changed your ways. That is VERY relatable to the average American. Many of us could find an example and say "Yeah, I remember doing that, that was stupid. Didn't do that again, and now I'm a better person for it."