Extra Text in Pingbacks

Whenever I post a pingback these days, I end up with extra text in the pingback comment that appears on the target blog. For example, the title of the previous post may appear, followed by the title of the appropriate post and some text.

How do I customize the text that is “sent” for a pingback or trackback. I’d really like to just send the title, if that’s possible, but I don’t know where to begin making changes.

Thanks in advance.