The title pretty much sums up my question. Is it ok to ask for an upvote when the OP feels his/her question deserves one?
It is acceptable only if the OP has done his/her best to formulate a concise, clear and well researched question.
On the other hand, if the question is unclear, lacks details, contains spelling, grammar and punctuation errors, and wrong tags as well, then it is not acceptable to ask for an upvote. In such cases, the OP must be advised to revise the question to make it clearer, useful and answerable.
Frankly, I would rather edit the question myself than upvote it to get it noticed.
In most cases we generally don't encourage this (though we don't discourage it either - and I'm speaking from the standpoint of experience in the community).
It is okay so long as there is a good reason for asking though, such as if the question needs to get more notice, or if the question is well worth the vote, such as in the case of "canonical" questions.