What is the general feelings about editing a poor question to include the missing actual question? This is guessing the posters intent, and could go wrong...
The approach here varies depending on the question.
In cases where the question seems clear, editing to include the question is an excellent approach, especially when the user may be new and unfamiliar with Stack Overflow or even how to edit question. Likewise when the OP has included the question in the comments in response to someone's "What is your question" comment. Usually when I do edit, I'll leave a comment explaining to the OP what I did:
I have edited your question based on x [your comment, what I think you are trying to say, etc]. However, if I have misinterpreted your needs, please feel free to edit your question yourself by clicking the edit button just below the text of your question.
The last portion about how to edit, I probably would only include if it is a brand new user that does not have an Editor badge.
Now in cases were it is impossible to guess, or you are split between 2 or 3 different possibilities on what the OP is asking, then the editing route is very risky and probably not worth it. This is especially true if you plan on answering or someone else has answered, because if you get it wrong, you open up the answers to undeserved downvotes (if there is an answer that answers the wrong question, a heads up via comment to the poster of the answer to let him know of the edit might be a friendly idea too).
In the cases when the question is not clear, the only choice you have is to comment. But I would try to go beyond the general "What is your question" comment and maybe try to explain to help guide the OP properly. Something to the effect of might be help
Your question is not very clear. Please try to clarify it by editing your post. From what I am reading, I think you are trying to ask x or y, but it you could confirm, it would be helpful in getting your question answered.
Then once the question is clarified, just hope that the edit (whether yours, the OP's, or anther user) is good enough to stem the tide of downvotes or close votes. If the question is not brand new, editing will also bumping the question to help get more attention and possibly attract a few upvotes, and if it was already closed, editing should also let it enter the reopen queue to see about reopening it.
To address your last point, upvoting just to balance downvotes is not a valid approach in my opinion, I would only upvote if I feel the question is worthy of an upvote. If several people vote just to balance downvotes and then 2 or 3 downvoters undo their votes, you could end up with a question that has a much higher score than maybe you think it deserves. However, assuming the edit is good and the question is clear, the question should be worthy of an upvote.