You think it's a good idea for parents to give kids a sip of beer, or puff of a cigarette, just to solve their curiosity, so they won't go out and try it themselves?

Depends on the kids, their peer group, the parents, etc. If the parents are good models as far as responsible use of alcohol, then I see no problem. If their drunks and condone that sort of behavior, I do see a problem.

As to smokes, never, ever a good idea.

You think it's a good idea for parents to give kids a sip of beer, or puff of a cigarette, just to solve their curiosity, so they won't go out and try it themselves?
I would have to say no. They are both very bad habits. Not too many people I know, want their kids to grow up to be smokers or alcoholics.