And no i don't mean the crutches that help one to walk!
I mean their gestures, movements that are idiosyncratic to your characters.
Do you have lots of shrugging, huffing, or frowning?
Julie Coulter Bellon has a great post here about this, which she found on Jordan McCollum's blog.
One of the commenters on Julie's blog mentioned a great book "The Emotional Thesaurus" which may prove useful to help explain your character gestures, instead of restricting it to a few. I think i'll get that for my kindle (really, i just love my new kindle so any chance to get a new book for it!).
So, pull out your manuscript, read through a page or two and see if you have repeated gestures or crutches, then 'find' them all and see if you can make them better.
This is a great way for your readers to see what the characters are thinking, even if they don't say it, or say something completely contradictory!