Just had one of those again.
I'd pretend I'm not home, but what if it's someone who doesn't want to sell me stuff? Maybe it's someone who needs help with something. Or what if they have a package for you? Can't just not open the door.
Because it's a crap job and they probably get bitched at most of the time, I always try to get rid of them nicely, but that usually takes a while. I need to learn to say right away that I'm not interested. Dammit.