What you would say would have to be something that you feel is good for you and something that you _know_ you are able to stick with.
Some here have said- no alcohol in the house, or not when the kids are up- or not at all ever. These choices are yours to make.
The consequence....what happens if the boundary is crossed has be what you feel is right. My idea is that it should 'fit' the situation or relate to it according to the severity of the boundary.
Although it's not my job to punish another, when the boundary is crossed I will act differently in some way or put in place another restriction to keep my life peaceful.
Nobody can know how another will react to boundaries or if they will deliberately cross to test them, that's why it has to be something you can stick with...or it's all for nothing and you end up with less respect than what you start with. I heard this in Alanon:"Say what you mean, mean what you say, but don't say it mean."
I recommend you read the book that Nuudawn recommended, I think you will find what you are looking for there.