Ideally the posters should be applying the homework tag themselves, but if I see a question that looks like a homework question what should I do?
You may edit in the homework tag (suggested edit if you don't have the rep) if you see a post like this. The important thing is that if the post looks homeworky to you, then check if it obeys the homework policy (it should show some effort on the OP's side, highlight the concept, and mention the OP;s level of understanding). If it doesn't, flag as "too localized", and leave a comment telling the OP how to make it fit the policy.
This is the comment I generally leave (with an optional "Welcome to Physics.SE!"):
Of course, that's a more moderator-y message, so I suggest you try something akin to this: