Work with an image.
Mike Wu and I had a class this week working on a two-character dialogue assignment. Everyone in class did very well with week one as far as the blocking they showed. Most of the shots the students showed were very clear , but what was consistently lacking was the performance oriented details. Much of this comes from relying on the line read and not exploring much further beyond that. The line read is only going to give you so much. Mike always says, "Lead the line. Don't let the line lead you". You have to fully know and understand a character in order to give a convincing performance. We segued this idea into showing some Mr. Bean footage to illustrate our point. I personally feel that Rowan Atkinson is one of the top 5 physical comedians/performers of all time. In researching him and his inspirations, I came to learn that Rowan always envisioned the behavior and mannerisms of Mr. Bean to fall in line with those of a mischievous 9 year-old boy. What a wonderful springboard to launch from. If you have a clear vision in your head as to who the character is, or what you think he/she represents, this then puts you in a better position to latch on to an image of something that can help steer you toward making interesting choices. These may manifest in body language, expression, or gesture. The more you bring to the party before you've picked up your mouse, the better your animation will be. 2-D, 3-D, or live-action,..... if you don't know your character you're screwed.
If you have a character oriented assignment/challenge that you seem to have a hard time overcoming, revisit or create a backstory for the character and give yourself an image that will help shape the mannerisms and performance of who you're animating. Doing so will help you to make unique choices, steering you away from animation cliches and provide you with fertile ground to plant an interesting, organic performance. Be it a 9 year-old boy or a pneumatic drill, an image can help shape a good piece of animation into a performance that brings a character to life.