For those with enough reputation, vote to to close the question. For those without this reputation, flag the question. I am on cstheory at least once a day (usually much more often) and check the flag and close queues; Suresh and Lev are also around.
I normally don't migrate a question to CS.SE unless I am the 5th close vote (I count flags as virtual close votes), because we want to encourage the community to self-moderate as much as possible. However, for obvious cases, I usually write something like:
This question would probably find a better home on CS.SE, if you want it migrated then flag or comment to let me know.
If the OP then flags or comments, I migrate right away.
If you get to a question before me, and want to comment (I highly encourage this, and a lot of people have been doing a good job of this. Thank you!) then please encourage the OP to flag their post for migration so that I can do it before waiting for 4 close-votes/other-user-flags.
However, only do the above in clear cut cases and for questions that would be an alright fit on CS.SE. Some of the bad questions we get are a bad fit not just because they are non-research level or non-theoretical, but simply because the asker put in zero effort in making themselves understood. Such questions are just bad questions, and we shouldn't send them to CS.SE but just close (and down-vote) them here.