step one: be foreign. this pretty much works for me.
one day i came home to a business card slipped in my mailbox. i ignored it.
the next day, as i was walking home, a man passed me on the path and asked politely if i was miss carroll. after my affirmative (i was all excited to get a package or something), he launched into a marvelous self-introduction characterized by polished bows and all the grandeur he could muster on a cheery spring day halfway up the hill to my house. he was a banker, my banker, apparently. my banker who rides a moped (snicker). he wanted to tell me some marvelous new thing to do with my money or maybe how to get the whitest whites, but my blithely uncomprehending face put him off pretty quick, and i've never heard from him again.
this was equally effective against the jehovah's witnesses.