I have been forcing myself to outline before I begin writing. It's really hard though. I feel outlining is the hardest part because you have to make all of the decisions right away, even if you change them later. I can take a very long to make and commit to a decision. But once I outline, writing is much more fun.
Act 2 (or 3 if five act pilot) is the hardest to outline and write. I always know the beginning and end before the middle.