I like stories and numbers. Especially numbers that tell stories. I've always liked the idea that "What gets measured gets improved".
I capture my data with a few apps/tools, Goodreads, Garmin and Trakt, and transfer them to my own spreadsheet.
Here's some of the things I've been tracking. My runs and the books I read, covering the physical and mental areas of my life, for improvement. Others, like movies watched, simply for fun.