All the mapping basics were from the HEK tutorial. I'd never modded for any game before Halo, so getting used to all the tools took a bit of time. The stuff I'm doing now is all just created through tinkering. Then engine has been able to handle this all along, I've just taken it a bit further.
I remember in 2004 when I was making Siege, no-one was working with bumpmapping, so I just looked at how it was done with the HEK stuff we were given and then expanded on it. Same with the cubemaps now, the example shaders basically show you how it's done.
One of the chapters in the Black Arts book is actually based on my tutorial.
