Learning a new graphics API

Hi, I'm teaching computer graphics and OpenGL at a university. Thus I often think about what the most motivating way are to teach this kind of stuff. Maybe you can give me some input on what you would prefer? Note that here I don't want to limit the options to a strict class-like setting! It's about learning in general. Given enough useful answers, I will share the findings publicly of course. Just check me Twitter stream: @renderpipeline .
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    A class (face to face, homework)
    Official specifications / API reference
    Written online tutorial
    Video tutorial / recorded lecture
    Live coding event (Twitch etc.)
    A book
    Asking/Googling specific questions
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