I started my career as an Assistant Account Executive at the Houston branch of Ogilvy & Mather Advertising. I had huge responsibility and no authority. Managers would frequently use AAE's as a go-between in their efforts to influence another manager. As in, "Go tell the Creative Director that the client wants to see at least four alternatives." I quickly figured out that I needed to convince the Creative Director that it was his idea to show the client four alternatives. But I wish I'd had this technique. I think it would have been faster.
The technique is that when someone balks at a request, ask them how much they feel like doing it on a scale of 1 to 10. The source is a book called Instant Influence. I especially like the fact that it gets you out of the habit of guessing someone's motivation. You will probably guess wrong.
If you ask, ‘Are you going to take my suggestion, yes or no?’ they continue to keep their motivation hidden. But if you ask them the ‘1-10’ question, they’re much more likely to reveal their motivation by saying a 2 or a 3, which is far better – you’ve now moved from a ‘No’ to at least a ‘Maybe.’