As a quick post-script on my last post, here's another general principle of prospective-grad-student-advice-giving. Don't tell prospectives to "think very hard" about grad school, unless you tell them exactly what to think about.
This one really picks my ass. By most accounts, pure rational cogitation couldn't even get Descartes out of his own fucking head. It's sure as fuck not going to tell prospectives anything about grad school.