I think you just have to set THE EXAMPLE. If you smoke weed, pop pills and drink in excess you can in most cases expect your kids to do the same but not always.
I don't think you can hide it from them and this sets up a thread of dishonesty if you try hidding it. Comunication is your best friend here...
My kids have always known I smoke...I mean when they were old enough to know. I don't smoke in the room with them as this is just rude....it is the same as cigarettes if you don't smoke it you don't like the smell...and out of 4 kids only one smokes weed, he has done X once and nothing else and he does not drink at all.I am much happier that he does not drink as you can die from alcohol no one has died from weed. As with anything moderation is the key and I have always stressed that.
my 2 cents anyway good thread...thanks

Cat