I'd very much like to contact Joss Whedon, to get some quotes or even an e-mail interview, for a tribute to Buffy which we are preparing for the next issue of a Greek science fiction magazine. I have tried to get in touch with people who have worked with Whedon, such as Jane Espenson and Doris Egan, but no luck there.
The correct process for contacting any of these guys is: call the WGA and find out who their agent is. Call the agent and find out who the publicist is, or who handles publicity. Call the publicist and explain your deal.
You may or may not get a response. Joss is, I am sure, deluged by requests for publicity. You might be better off hitting one of his writers, such as Jane herself. If you're a Lostie, Javier Grillo-Marxuach (Supervising Producer on the show) is semi-reachable for publicity purposes; he's got a blog, hasn't he? J. J. Abrams is likely to be way too busy.
Also, Joss really gets no benefit from a Buffy tribute. He's probably moved on. If you wanted to ask him about his next project, he'd probably be more interested.
People in TV tend to be really busy all the time. They only promote stuff when it's what they're doing: when a show is coming out.
And as I write this, I'm looking down at the pool from the tower room where I'm working, and watching a brown-and-orange box turtle sitting perfectly still looking at some impatiens, pondering his plan for the rest of the day.