This should be common sense, but it seems for many parents it's not.
Don't try to keep your kids from doing something you yourself are
doing, that applies to drinking, smoking, extra-marital sex, whatever kind of thing it is doesn't
matter, just don't.
Saying "I pay the bills I make the rules"
is a legal augment not a Moral one. Forbidding someone to do something
your doing is the definition of hypocrisy, period. But it's not even a
good legal argument, a just ruler follows the rules they expect their
subjects to follow.
The most effective way to encourage whatever Morality you believe in is to lead by example.