A good way to test and see if you've got social proof, from my experience, is that when you're watching a some sort of entertainment (e.g., a movie, a stand up comedian etc.) especially some sort of entertainment that involves comedy, people around you will look at you after the punch line to see if you thought it was funny and to see if you're laughing. It's as if they're asking for permission to laugh. I don't know if anyone else notices this sort of thing, but I find it's a pretty strong indicator.

Secondly, a little tip I've implemented into my daily conversation is to never have the last word in a conversation (or a conversation thread). That is, never be the last person speaking. When you choose not to speak last, you are deciding to stop speaking which puts you in the position of power. It also makes the other person feel slightly, though not overly, self conscious. Don't overuse this one or make it seem to obvious though. It's especially good for phone game.

Edit:

I remembered another one: The manly pause. Whenever someone asks you a question or tries to get your attention don't respond very quickly. It makes you look like you're a butler catering to them. Take a pause, formulate your sentence and then answer slowly and clearly. For example, if someone says your name in order to get your attention wait for them to say it at least twice before you turn and look. This sort of thing falls into the attitude of being nonreactive/proactive.

Thoughts?