When I first learned about boundaries and started setting them, I wrote them out first, practiced saying them, and then sat him down and communicated them. Here's how it went:
1. When you come to see me drunk or on drugs, I feel angry and upset. I do not want to have people in my life whose behavior causes me to feel angry and upset.
2. Therefore, if you come to see me and you are drunk or on drugs, I will not talk to you and I will not allow you into the house.
3. I would like for you to not come see me if you are drunk or on drugs.
4. Do you understand? Please repeat back to me what I just said.
That's it. I provided no opportunity for him to argue with me about anything I said about my boundary. I said Thank You and got up from the table and walked away. Then, whenever he came to the house drunk or on drugs, I did exactly what I said I would.
I also set a boundary concerning phone calls. Basically the same thing as above but my requirement was that he not call me after 6PM any day of the week, and if he did call me after 6PM, I would not talk to him and would immediately hang up the phone. The reason was I could never predict whether or not he would be high or drunk when he called, and when he was high or drunk I would get so flippin' angry I would start screaming into the phone and then would be hyper and not able to fall asleep in time to get enough sleep so that I could get up early and go to work the next day.
Another boundary I set concerned him having sex with other people. I knew he had had sex with two other people during the time he supposedly was in love with me and wanted to marry me, quack quack, and I was tired of the rollercoaster ride. So I told him my boundary, which was, if you have sex with one more person, I will no longer act as your "girlfriend" and I will exclude you from my life. He did and I did.
When I first started my boundary work, I was hurt, scared, and actually shaking as I read my boundaries off to him. But with time, it got easier and in the end I was all the more stronger for it. It feels REALLY good to communicate your needs to another person and then STAND UP for yourself and your needs without screaming, crying, or throwing breakable objects in expression of your anger. And the success I experienced in THIS relationship translates over to my other relationships now too.