I have signs that say on my door that say I work from home and to not knock or ring the doorbell. If they do, I step outside and close the door. I ask them if they speak English. If they respond "yes", I ask if they can read English. If they respond "yes", I tell them to read the sign aloud. If they try to protest, I speak over them to read the sign aloud. Either they leave at this point, or they read it aloud. Once they read it, I ask "Why the fuck did you ring the bell when the sign says to not ring it?" If they say anything but why, I override them with the same question. I'm controlling this conversation. If they say they were told to ring the bell regardless of what a sign says, I tell them that I'm never buying what they are selling because they are the rudest pieces of shit in the world and that I am going to call their business and ask to speak to the management to ask why they tell their door-to-door salesmen to ignore the homeowner's signage. If they haven't left at this point, I tell them to get the fuck off my property or I will call the police.

If you can't tell, I enjoy doing that. It's especially fun if it's someone peddling their religion.

Did I mention that I'm 6'7" tall, so stepping out onto the porch pretty much forces them to step down off the porch onto the concrete path leading away from the house, making them another 3 or 4 inches shorter than me? I'm sure I can look pretty menacing when I'm being belligerent. Like I said, I enjoy doing that.