Baby-boom parents who experimented with illicit drugs in the 1960s and '70s are facing the difficult task of persuading the children of the '90s not to follow their example. Antidrug experts say that strong parental disapproval - not only of illicit drugs but of tobacco and alcohol - is one of the most effective tools in countering drug use by teens. They advise parents to talk to their children about the dangers of drug use. They suggest that it may be necessary during such discussions for parents to admit any prior use of illicit drugs. But is it a good...