I've watched the first two parts of this 5.5 hr. series of 3 so far. They've been excellent as usual from Ken Burns and very educational (and relevant to recent issues in the U.S.)
I watched it on my PBS app (free) on my iPad, but it's on their website as well as on TV.
http://video.pbs.org/video/15393956 for part 1...1) Read the instruction manual2) Read an additional instruction book3) Read about it online4) Watch a video5) Take a workshop or class in person6) Take a workshop/class online7) Go to a convention or trade show8) Hire a personal tutor9) Read (camera specific) forums10) Visit a manufacturers online learning center11) DIY/hands on- test functions and learn by doing it12) Network with others with the same or similar equipment. There's groups for both in-person meet-ups and virtual groups.