I'm not very clear on when we should vote to close a question and when we should flag it.
Context: I see an exact duplicate question and vote to close it so that it doesn't get added to, and also flag it so that moderators can delete it.
Is this the right action to take?
You should always vote to close. Stack Exchange is designed to be moderated by the community -- specifically, those users who have earned privileges by posting great questions and answers.
Flagging down a ♦ moderator is a stop-gap that will become mostly unnecessary as the number of users with 500+ rep increases. We're not quite there yet, so go ahead and flag when it looks like the question won't get closed in a timely manner otherwise.
Vote to close if you believe that the question should be closed simply because it does not work well as a question. If you think that moderators need to be involved - that is, if you think the posted is spamming or if the question need to go to another forum.
UX is less likely to be spammed than the main SO board, and the mods really don't need to be involved much, so use your vote to indicate that you believe the post should be closed.
Flag when:
you feel the situation is urgent
you feel extremely strongly that something is wrong
In all other cases, use the other tools you have: voting, commenting, editing, etc.
