EDIT: If you like this journal entry, check out The Sarcastic Guide to Writing ebook http://www.amazon.com/The-Sarcastic-Guide-Writing-ebook/dp/B005TOCC1C for exclusive content on world-building, character, and dialogue!
Sorry for the delay; I attended the Austin GDC ... whoof. Still tired.
1. Mediate your characters emotional responses. I see this a lot, and it reads like bipolar disorder. The character exalts in their laughter, achieving tears of mirth, and then in two sentences manages to burst into the other kind of tears. The bad kind. Conversely, theres the character who doesnt care about anything, even kittens.