A series of tricks and techniques I learned doing tiny GLSL demos

I'm oddly fascinated with GLSL shaders recently because I've been trying out a terminal which supports shaders. I have currently applied a retro terminal shader and love using terminal this way.

What's a good way to get started learning to build/customize shaders with GLSL? I have an engineering math background but I was never the best at math. And GLSL syntax looks a bit tedious to be honest, but I'd love to dive in.