In case you're new to the craft of writing, let me explain: When you're in one character's PV and you want to get something across to the reader about the emotions of the non-PV character, basic body language is a great help. Clenched fists, furrowed brows, a flex of the jaw, eyes cast downward--these are all great non-verbal, non telling cues. And we all know what they mean when we see them. (I realize I rushed that explanation; if you want to know more, I'd be glad to post a longer blog about it. Just ask.)
I recently found a site on YouTube that takes videos clips of famous (and infamous) people and dissects their body language. I warn you, though, it's addicting! I highly recommend it if you struggle with showing rather than telling, or if you just want to take your body language skills up a notch.
I hope you find it fun and informative.