Often graduate students ask me for a good problem to work on. This is
one of the biggest challenges of an advisor. A good problem for a
graduate student must fulfill each of three characteristics.
Open.
Doable.
Interesting.
Finding problems that
fit any two of these three is not hard, but if a problem is doable and
interesting, someone likely would have solved it by now. Too often
interesting is the property that is given the least emphasis.
I
generally give the advice that my advisor, Michael Sipser, gave to
me. Pick up a proceedings of a recent conference in your area and read
through the abstracts of papers until you find one that interests you.
The "interests you" part is important, for without it you
won't have the motivation to study further.
Read the paper thoroughly. Read related papers. If you lose interest,
start the process all over again.
Once you've read several papers in an area that interests you talk
about it with your advisor and your fellow graduate students. Some of
these papers might list open questions and you could work on
those. You might say, "Karp listed this as an open question, and
if Karp can't solve it why should I be able to?" Karp is a very
smart but also very busy person. It is unlikely he spent more than an
hour thinking hard about these questions. As a graduate student you
can spend much more time focusing on these problems and could easily
make more progress than someone like Karp could.
Even better is to formulate your own problems. Perhaps there is an
interesting variation in a model that the original paper, for whatever
reason, did not cover. Perhaps you can find connections between two
papers that no one had noticed before. These are great problems to
work on: As you are breaking new ground, theorems can start flowing
like water. Just remember not to have too much weirdness in your
questions; keep the research interesting.