YouTube Insight is a free analytics tool that helps you better understand how the YouTube community is interacting with your video and grow your audience. So how do you master this "science"? First, let's start with the basics. Monitoring viewing trends through Insight's "Views" tab can help you nail down the best time to upload your new videos. There’s more sophisticated features, like "Discovery," which shows you how your viewers found your videos (i.e., through search, an embedded player, related videos or viral sharing). Using "Discovery," you can also see which keywords are driving views and then advertise against these keywords using YouTube's Promoted Video product. "Hot Spots" feature helps you understanding which parts of your video people liked. You can even export your data into a CSV files.

Source:→ Google Blog