Everywhere! I have a giant folder of all sorts of references, both from artists and real life (it’s ~30gb of pictures). If I’m stuck I just look through them for some inspiration. More often than not I just put pencil to paper and mess around until something interesting comes out.

A lot of varied practice. Don’t just focus on one thing. Be a stereotypical artist and carry around a sketchbook everywhere. Don’t be afraid to learn from/emulate other artists (just don’t rip them off, obviously). Get feedback and criticism (not just blatant asskissing, you’ll never learn that way).