The way I understood it was that Libertarianism was trying to remove a lot of the government's influence on people, and letting us work things out on our own.
For instance, seat belts. Currently, we have government-instituted laws that make driving without a seatbelt a punishable offense. Libertarianism would abolish the belt law, and instead leave it to the person driving to decide whether or not they wanted to wear one or not.
It's based off of trying to get rid of the pervasive and sometimes unnecessary laws that are running around, in the belief that people have the common sense (or at least rational thinking) to do what's best for them anyways.
Nothing wrong with educating someone about the dangers of driving without a belt. By all means, make it blatantly clear what will happen if you do something like that. But don't try to turn it into a criminal act.
I'm not sure how it reflects on smoking/driving/drinking/sex ages, as those are based on "age of reason" requirements rather than just trying to "coax" people into something...
But that's the basic gist. Don't try and prevent us from doing things in our own personal lives. That's our business. You make decisions on your business, and I'll make decisions regarding mine. Leave me alone. And if something bad happens to me because I did something stupid, well, I had it coming.