How to Deal With Those Pushy Door-to-Door Christians etc

I'm one of those people that believes everyone deserves some amount of respect and I CERTAINLY do not like to be rude or disrespectful if it is not truly warranted, but I find it difficult to turn away someone who is from one of those groups where they must visit you door-to-door or stop you on the street to tell you about "THEIR" beliefs, not taking into account your own feelings, only their own and what potential good they can do for "THEIR" cause and mayhaps help another person like themselves.

I've had one good "Street" experience where a Christian on the street wanted to talk to me about his beliefs and I simply replied with a smile, since I was in a hurry for class and had no time to be stopped by the man, "Sorry but I've found my own path." Because I was quite happy, content, and in a blissful state of mind since I had found my path around that same time.

As for Jehovas (sp?) Witnesses and the like what should one do? How should one approach this situation? It feels like they hardly give you any room to interject and to simply slam the door in their face or ignore them is rude without honestly and openly telling them, "Hey you have your path and I have mine, I have found peace in that path and happiness. Please leave me in peace." But I noticed that if you pull anything remotely like that they just simply can't go away. No; they want to chat with you for an hour trying to convince you their way is best. *sighs* It's a very frustrating matter I find. Any ideas or suggestions you would like to share would be appreciated.