OP said hacking, when I think gaining super user I think of rooting. I was under the assumption that OP knew about and what rooting was, so I supplied a more security related answer. Even though gaining root is a hack, I hear the term "rooting" instead of "hacking" associated with any privilege escalations. But all in all, replies supplied are all correct. It all depends on what your wanting to do.
@Kulver:
I built a beige box once, on them old ass phones in my area that people still use, it was fun while it lasted. And actually phreaking, at least the hardware side, got me into hardware even more. The anarchist cookbook was my ref, and at the time I thought it was the shite. Still, Jolly Rogers might help out in the zombie apocalypse.