Ok, I don't get trackbacks.

Well, I understand the basic idea. I write something, maybe quoting someone else's blog. I send a ping to that blog saying "hey, I'm commenting on you." They should then be able to come see me and what I said. kind of a referer system... kind of.

Anyway, I don't get the implimentation. I have the auto trackback feature enabled but MT doesn't ever seem to use it. If I try and manually create a trackback ping, I obviously don't send it to the right place, as I get a ping error in my activity log. If I have linked to a permenant link on someone's page, isn't that the http ref I should use for a trackback ping? And if so, why do I get an error. And if not, what should I use?

Thanks,

James