The only way to learn is not to learn at all... no wait, thats the only way to win by not playing.
Things now days are complex and you can write huge code that does nothing more than control a simple 3D object, to really learn and to learn to code well in small space get old skewl. Pick up a C64 or an Amiga A500 and learn to code on one of those.
Who doesn't like a 45min mega-demo packed on 2 800k floppies?
Don't look. Start. The only way to make demos is to have an idea. There are no tutorials that will show you how to make demos. There are some articles on some diskmags.
Just learn OpenGL or DirectX and make demos. The demo is all arround you. You just need to push it outside. You've got to find the path alone.
The most important: DON'T USE DEMOTOOLS. I REPEAT: DON'T USE ANY DEMOTOOL. YOU ARE YOUR OWN DEMOTOOL. USE YOURSELF.
hei, if it worked for a bastard kid to blow up an universal menace the size of a moon with a couple blind shots it can certainly help you make some cubes rotate on the screen.