This is very much dependent on the question and the poster. There are some questions which look like high school homework problems posted by users who are new to the forum. These are usually quickly dispatched, although a leading question in a comment may be a public (dis-)service. There are some questions which look like homework or show a serious lack of understanding, but are posted by a user of some standing and history. A recent one went from a vote score of -3 through some edits to a positive score when the question morphed into something that got a lot of positive consideration from the community. If you want to give the user some slack and some time to improve the question, a guiding comment followed by some patience is a strategy I use. If the question just looks out of place, a comment as to why is appreciated.
I have seen too many questions on this forum closed by those who did not appreciate the contribution such a question gave to the forum. I have left comments asking why and asking for reconsideration. I feel that there are enough active close voters in the community, and not enough explanation. I recommend flagging if it is really important, and otherwise commenting to guide or inform the user about forum standards. I have yet to vote to close a question.
Gerhard "Did Register To Vote, However" Paseman, 2017.01.24.