I'm an in-house UX Designer for a medium sized company, and big part of my job is building wireframes for inclusion in spec documents. Usually, the workflow goes something like this - the product manager will come up with the new feature/improvement, I'll work up the mockups, and we'll get back together to discuss along with IT before the spec is finalized. The wireframes are usually low-fidelity in something like Balsamiq Mockups, but occasionally they are full on Axure or Justinmind-style interactive prototypes.
Onto the question - when presenting a set of wireframes, should I send the wireframes ahead of time or not? As a receiver of meeting requests, I always appreciate as much information up front as I can possibly get. But as a giver of demonstrations, I understand that wireframes don't always make much sense without the presentation.
So what are the situations where you'd want to send wireframes ahead of time?