I'm drafting for the first time in a while, so my mind is on effective writing techniques.
I read this great post by Nicole Steinhaus at YA Stands last year: Action Speaks Louder Than Body Parts. Nicole was working as a literary intern and noticed writers using an awful lot of physical reactions to indicate how a character was feeling or reacting to events in the story. Examples: someone's heart pounding, knees going weak, palms, sweating, or brows furrowing.
In the article linked above, the author makes some good points (with examples from John Green's truly excellent Looking for Alaska) about why action that shows a character's response is often much better.
This is a particular weak point in my writing, so I'm going to pay more attention to it in the future. At the very least, I'm going to make sure to avoid cliché physical reactions like hearts slamming against chests and (a personal favorite) letting out breaths the characters didn't know they'd been holding.
That's not to say that there's no place for telling the reader what physical reactions the character is experiencing--after all, it is showing rather than telling (although this post makes the point that it's just a different kind of telling, and I sort of agree). But the writing can often be more effective if the body part action is kept to a minimum.
In case you're still on the fence, I leave you with this post from former lit agent Mary Kole: Physical Clichés.