After I got the fundamentals down, I turned my focus to acting. I mean, acting is what we do, so why wouldn't I study it seriously like any other professional actor?
I started by studying Stanislavski. I have a book of his that has a bunch of assignments in it. Like...go to your bedroom and pack a suitcase. Now, pack the suitcase like you're going off to war. Now pack it like you're trying to leave your lover who just stepped out for a moment and you want to be gone before he/she gets home. Now pack it like you're being evicted. Stuff like that.
I also spent some time at the Lyric School of Acting in Vancouver, BC. It's interesting how similar my first animations were to my first live acting assignments. For starters, my hands were way too busy, and I would just stand there waiting for my line. But eventually we started working on subtext, backstory, and ways to really own your character. I recently read a quote by a screenwriter that went something like, "I wanted the audience to get to know my character quickly, so I had him pull a used paper filter out of the coffee maker, rinse it, and reuse it."