My current favorites:
“Think hard. Be honest with yourself. Are the stakes in your current manuscripts as high as they can possibly be? Can you define the stakes right now? Can you point to the exact pages in which the stakes escalate, locking your protagonist into his course of action with less hope of success than before?” – Donald Maass – Writing the Breakout Novel
“Think of your novel as “A Life: The Good Parts Version.” All the sex and violence, passion and struggle. None of the teeth brushing.” – Holly Lisle.