"Hi, my name is xxxxxx, I know you don't appreciate me coming here uninvited, on a Saturday morning no less. You were probably hoping to relax after a hard week of work. What's that like, by the way, working a full-time job? Never mind, I'm getting side-tracked.
"The reason I'm here is that I belong to a very bizarre religion that requires all it's members to go from door-to-door peddling their literature. If you could just take these two magazines I have in my hand, I will be on my way. Feel free to throw them in the trash as soon as you get inside. That's what I do with all the excess ones I can't get rid of. I just want those people in that car over there to see me presenting these to you. If that doesn't work for you, just look really angry, pretend to raise your voice, maybe stick a finger in my face for posterity. Then finish it off by slamming the door in my face."
Of course, this was only effective when I went to the doors by myself, or with someone with my same level of zeal.