Much of this kind of advice is from academics and other such ex-grad-schoolers. Here's an awesome essay from a current grad student: Graduate Student: To Be or Not To Be; published last month in the IIT-B Student Magazine Insight, it's by Karthik Shekhar, an alumnus who is now doing his PhD at MIT. Some excerpts:
Now back to what’s different about research – exams and quizzes are like short sprints but doing scientific research is the equivalent of running a marathon. You can maintain an extremely unhealthy lifestyle and impress your friends by outrunning them in short sprints thanks to your height or long legs (or vitamin supplements) but you cannot fluke a marathon. Analogously, many of us at the IITs have been ‘nurtured’ to cram lots of information  with little or no deep understanding, and reproduce it in a three-hour sanitized setting but real research is a different game. [...]
Most important lessons of life are learned in the gut, not in the brain . It took me two and a half years into my PhD to understand that my IIT degree, despite its bells and whistles, had left many gaps in my education and work ethic that needed desperate attention. [...]
The footnote #2 in the text takes us to this:
 The coaching class empires are to be held singularly responsible for this malady. Yes, I think it is a malady.
Here's his very good advice on picking advisers:
... It is extremely important to pick an advisor who is concerned about your intellectual growth and not just your productivity. Students who are starting up are often swayed by credentials and fail to evaluate the human side of the research advisor: of how flexible he/she will be to your needs and whether you can look up to him/her as a mentor?
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Thanks to Deepak Malani for the link.